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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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9722c2dac7
Thomas Hellstrom bisected a regression where erratic 3D performance is experienced on virtual machines as measured by glxgears. It identified commit58d081b5("sched/numa: Avoid overloading CPUs on a preferred NUMA node") as the problem which had modified the behaviour of effective_load. Effective load calculates the difference to the system-wide load if a scheduling entity was moved to another CPU. The task group is not heavier as a result of the move but overall system load can increase/decrease as a result of the change. Commit58d081b5("sched/numa: Avoid overloading CPUs on a preferred NUMA node") changed effective_load to make it suitable for calculating if a particular NUMA node was compute overloaded. To reduce the cost of the function, it assumed that a current sched entity weight of 0 was uninteresting but that is not the case. wake_affine() uses a weight of 0 for sync wakeups on the grounds that it is assuming the waking task will sleep and not contribute to load in the near future. In this case, we still want to calculate the effective load of the sched entity hierarchy. As effective_load is no longer used by task_numa_compare since commitfb13c7ee(sched/numa: Use a system-wide search to find swap/migration candidates), this patch simply restores the historical behaviour. Reported-and-tested-by: Thomas Hellstrom <thellstrom@vmware.com> Signed-off-by: Rik van Riel <riel@redhat.com> [ Wrote changelog] Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140106113912.GC6178@suse.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
7380 lines
189 KiB
C
7380 lines
189 KiB
C
/*
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* Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
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*
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* Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*
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* Interactivity improvements by Mike Galbraith
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* (C) 2007 Mike Galbraith <efault@gmx.de>
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*
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* Various enhancements by Dmitry Adamushko.
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* (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
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*
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* Group scheduling enhancements by Srivatsa Vaddagiri
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* Copyright IBM Corporation, 2007
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* Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
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*
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* Scaled math optimizations by Thomas Gleixner
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* Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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*
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* Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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*/
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#include <linux/latencytop.h>
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#include <linux/sched.h>
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#include <linux/cpumask.h>
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#include <linux/slab.h>
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#include <linux/profile.h>
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#include <linux/interrupt.h>
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#include <linux/mempolicy.h>
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#include <linux/migrate.h>
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#include <linux/task_work.h>
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#include <trace/events/sched.h>
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#include "sched.h"
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/*
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* Targeted preemption latency for CPU-bound tasks:
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* (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* NOTE: this latency value is not the same as the concept of
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* 'timeslice length' - timeslices in CFS are of variable length
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* and have no persistent notion like in traditional, time-slice
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* based scheduling concepts.
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*
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* (to see the precise effective timeslice length of your workload,
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* run vmstat and monitor the context-switches (cs) field)
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*/
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unsigned int sysctl_sched_latency = 6000000ULL;
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unsigned int normalized_sysctl_sched_latency = 6000000ULL;
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/*
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* The initial- and re-scaling of tunables is configurable
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* (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
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*
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* Options are:
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* SCHED_TUNABLESCALING_NONE - unscaled, always *1
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* SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
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* SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
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*/
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enum sched_tunable_scaling sysctl_sched_tunable_scaling
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= SCHED_TUNABLESCALING_LOG;
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/*
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* Minimal preemption granularity for CPU-bound tasks:
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* (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*/
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unsigned int sysctl_sched_min_granularity = 750000ULL;
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unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
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/*
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* is kept at sysctl_sched_latency / sysctl_sched_min_granularity
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*/
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static unsigned int sched_nr_latency = 8;
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/*
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* After fork, child runs first. If set to 0 (default) then
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* parent will (try to) run first.
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*/
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unsigned int sysctl_sched_child_runs_first __read_mostly;
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/*
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* SCHED_OTHER wake-up granularity.
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* (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* This option delays the preemption effects of decoupled workloads
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* and reduces their over-scheduling. Synchronous workloads will still
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* have immediate wakeup/sleep latencies.
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*/
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unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
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unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
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const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
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/*
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* The exponential sliding window over which load is averaged for shares
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* distribution.
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* (default: 10msec)
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*/
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unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
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#ifdef CONFIG_CFS_BANDWIDTH
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/*
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* Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
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* each time a cfs_rq requests quota.
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*
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* Note: in the case that the slice exceeds the runtime remaining (either due
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* to consumption or the quota being specified to be smaller than the slice)
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* we will always only issue the remaining available time.
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*
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* default: 5 msec, units: microseconds
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*/
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unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
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#endif
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static inline void update_load_add(struct load_weight *lw, unsigned long inc)
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{
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lw->weight += inc;
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lw->inv_weight = 0;
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}
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static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
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{
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lw->weight -= dec;
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lw->inv_weight = 0;
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}
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static inline void update_load_set(struct load_weight *lw, unsigned long w)
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{
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lw->weight = w;
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lw->inv_weight = 0;
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}
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/*
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* Increase the granularity value when there are more CPUs,
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* because with more CPUs the 'effective latency' as visible
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* to users decreases. But the relationship is not linear,
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* so pick a second-best guess by going with the log2 of the
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* number of CPUs.
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*
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* This idea comes from the SD scheduler of Con Kolivas:
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*/
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static int get_update_sysctl_factor(void)
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{
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unsigned int cpus = min_t(int, num_online_cpus(), 8);
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unsigned int factor;
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switch (sysctl_sched_tunable_scaling) {
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case SCHED_TUNABLESCALING_NONE:
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factor = 1;
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break;
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case SCHED_TUNABLESCALING_LINEAR:
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factor = cpus;
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break;
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case SCHED_TUNABLESCALING_LOG:
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default:
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factor = 1 + ilog2(cpus);
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break;
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}
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return factor;
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}
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static void update_sysctl(void)
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{
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unsigned int factor = get_update_sysctl_factor();
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#define SET_SYSCTL(name) \
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(sysctl_##name = (factor) * normalized_sysctl_##name)
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SET_SYSCTL(sched_min_granularity);
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SET_SYSCTL(sched_latency);
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SET_SYSCTL(sched_wakeup_granularity);
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#undef SET_SYSCTL
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}
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void sched_init_granularity(void)
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{
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update_sysctl();
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}
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#define WMULT_CONST (~0U)
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#define WMULT_SHIFT 32
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static void __update_inv_weight(struct load_weight *lw)
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{
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unsigned long w;
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if (likely(lw->inv_weight))
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return;
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w = scale_load_down(lw->weight);
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if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
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lw->inv_weight = 1;
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else if (unlikely(!w))
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lw->inv_weight = WMULT_CONST;
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else
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lw->inv_weight = WMULT_CONST / w;
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}
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/*
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* delta_exec * weight / lw.weight
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* OR
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* (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
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*
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* Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
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* we're guaranteed shift stays positive because inv_weight is guaranteed to
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* fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
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*
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* Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
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* weight/lw.weight <= 1, and therefore our shift will also be positive.
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*/
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static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
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{
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u64 fact = scale_load_down(weight);
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int shift = WMULT_SHIFT;
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__update_inv_weight(lw);
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if (unlikely(fact >> 32)) {
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while (fact >> 32) {
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fact >>= 1;
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shift--;
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}
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}
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/* hint to use a 32x32->64 mul */
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fact = (u64)(u32)fact * lw->inv_weight;
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while (fact >> 32) {
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fact >>= 1;
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shift--;
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}
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return mul_u64_u32_shr(delta_exec, fact, shift);
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}
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const struct sched_class fair_sched_class;
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/**************************************************************
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* CFS operations on generic schedulable entities:
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*/
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#ifdef CONFIG_FAIR_GROUP_SCHED
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/* cpu runqueue to which this cfs_rq is attached */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
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{
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return cfs_rq->rq;
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}
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/* An entity is a task if it doesn't "own" a runqueue */
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#define entity_is_task(se) (!se->my_q)
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static inline struct task_struct *task_of(struct sched_entity *se)
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{
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#ifdef CONFIG_SCHED_DEBUG
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WARN_ON_ONCE(!entity_is_task(se));
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#endif
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return container_of(se, struct task_struct, se);
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}
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/* Walk up scheduling entities hierarchy */
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#define for_each_sched_entity(se) \
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for (; se; se = se->parent)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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return p->se.cfs_rq;
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}
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/* runqueue on which this entity is (to be) queued */
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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
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{
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return se->cfs_rq;
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}
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/* runqueue "owned" by this group */
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static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
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{
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return grp->my_q;
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}
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static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
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int force_update);
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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
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{
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if (!cfs_rq->on_list) {
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/*
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* Ensure we either appear before our parent (if already
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* enqueued) or force our parent to appear after us when it is
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* enqueued. The fact that we always enqueue bottom-up
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* reduces this to two cases.
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*/
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if (cfs_rq->tg->parent &&
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cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
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list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
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&rq_of(cfs_rq)->leaf_cfs_rq_list);
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} else {
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list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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&rq_of(cfs_rq)->leaf_cfs_rq_list);
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}
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cfs_rq->on_list = 1;
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/* We should have no load, but we need to update last_decay. */
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update_cfs_rq_blocked_load(cfs_rq, 0);
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}
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}
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static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
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{
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if (cfs_rq->on_list) {
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list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
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cfs_rq->on_list = 0;
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}
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}
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/* Iterate thr' all leaf cfs_rq's on a runqueue */
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#define for_each_leaf_cfs_rq(rq, cfs_rq) \
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list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
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/* Do the two (enqueued) entities belong to the same group ? */
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static inline int
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is_same_group(struct sched_entity *se, struct sched_entity *pse)
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{
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if (se->cfs_rq == pse->cfs_rq)
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return 1;
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return 0;
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}
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static inline struct sched_entity *parent_entity(struct sched_entity *se)
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{
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return se->parent;
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}
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/* return depth at which a sched entity is present in the hierarchy */
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static inline int depth_se(struct sched_entity *se)
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{
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int depth = 0;
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for_each_sched_entity(se)
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depth++;
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return depth;
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}
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static void
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find_matching_se(struct sched_entity **se, struct sched_entity **pse)
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{
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int se_depth, pse_depth;
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/*
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* preemption test can be made between sibling entities who are in the
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* same cfs_rq i.e who have a common parent. Walk up the hierarchy of
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* both tasks until we find their ancestors who are siblings of common
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* parent.
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*/
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/* First walk up until both entities are at same depth */
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se_depth = depth_se(*se);
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pse_depth = depth_se(*pse);
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while (se_depth > pse_depth) {
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se_depth--;
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*se = parent_entity(*se);
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}
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while (pse_depth > se_depth) {
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pse_depth--;
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*pse = parent_entity(*pse);
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}
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while (!is_same_group(*se, *pse)) {
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*se = parent_entity(*se);
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*pse = parent_entity(*pse);
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}
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}
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#else /* !CONFIG_FAIR_GROUP_SCHED */
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static inline struct task_struct *task_of(struct sched_entity *se)
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{
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return container_of(se, struct task_struct, se);
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}
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
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{
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return container_of(cfs_rq, struct rq, cfs);
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}
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#define entity_is_task(se) 1
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#define for_each_sched_entity(se) \
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for (; se; se = NULL)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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return &task_rq(p)->cfs;
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}
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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
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{
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struct task_struct *p = task_of(se);
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struct rq *rq = task_rq(p);
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return &rq->cfs;
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}
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/* runqueue "owned" by this group */
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static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
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{
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return NULL;
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}
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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
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{
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}
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static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
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{
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}
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#define for_each_leaf_cfs_rq(rq, cfs_rq) \
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for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
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static inline int
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is_same_group(struct sched_entity *se, struct sched_entity *pse)
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{
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return 1;
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}
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static inline struct sched_entity *parent_entity(struct sched_entity *se)
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{
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return NULL;
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}
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static inline void
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find_matching_se(struct sched_entity **se, struct sched_entity **pse)
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{
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}
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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static __always_inline
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void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
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|
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/**************************************************************
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* Scheduling class tree data structure manipulation methods:
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*/
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static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
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{
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s64 delta = (s64)(vruntime - max_vruntime);
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if (delta > 0)
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max_vruntime = vruntime;
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return max_vruntime;
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}
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static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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{
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s64 delta = (s64)(vruntime - min_vruntime);
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if (delta < 0)
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min_vruntime = vruntime;
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return min_vruntime;
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}
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|
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static inline int entity_before(struct sched_entity *a,
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struct sched_entity *b)
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{
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return (s64)(a->vruntime - b->vruntime) < 0;
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}
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|
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static void update_min_vruntime(struct cfs_rq *cfs_rq)
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{
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u64 vruntime = cfs_rq->min_vruntime;
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if (cfs_rq->curr)
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vruntime = cfs_rq->curr->vruntime;
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|
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if (cfs_rq->rb_leftmost) {
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struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
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struct sched_entity,
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run_node);
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if (!cfs_rq->curr)
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vruntime = se->vruntime;
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else
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vruntime = min_vruntime(vruntime, se->vruntime);
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}
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|
|
/* ensure we never gain time by being placed backwards. */
|
|
cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
|
|
#ifndef CONFIG_64BIT
|
|
smp_wmb();
|
|
cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* Enqueue an entity into the rb-tree:
|
|
*/
|
|
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
|
|
struct rb_node *parent = NULL;
|
|
struct sched_entity *entry;
|
|
int leftmost = 1;
|
|
|
|
/*
|
|
* Find the right place in the rbtree:
|
|
*/
|
|
while (*link) {
|
|
parent = *link;
|
|
entry = rb_entry(parent, struct sched_entity, run_node);
|
|
/*
|
|
* We dont care about collisions. Nodes with
|
|
* the same key stay together.
|
|
*/
|
|
if (entity_before(se, entry)) {
|
|
link = &parent->rb_left;
|
|
} else {
|
|
link = &parent->rb_right;
|
|
leftmost = 0;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Maintain a cache of leftmost tree entries (it is frequently
|
|
* used):
|
|
*/
|
|
if (leftmost)
|
|
cfs_rq->rb_leftmost = &se->run_node;
|
|
|
|
rb_link_node(&se->run_node, parent, link);
|
|
rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
|
|
}
|
|
|
|
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
if (cfs_rq->rb_leftmost == &se->run_node) {
|
|
struct rb_node *next_node;
|
|
|
|
next_node = rb_next(&se->run_node);
|
|
cfs_rq->rb_leftmost = next_node;
|
|
}
|
|
|
|
rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
|
|
}
|
|
|
|
struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rb_node *left = cfs_rq->rb_leftmost;
|
|
|
|
if (!left)
|
|
return NULL;
|
|
|
|
return rb_entry(left, struct sched_entity, run_node);
|
|
}
|
|
|
|
static struct sched_entity *__pick_next_entity(struct sched_entity *se)
|
|
{
|
|
struct rb_node *next = rb_next(&se->run_node);
|
|
|
|
if (!next)
|
|
return NULL;
|
|
|
|
return rb_entry(next, struct sched_entity, run_node);
|
|
}
|
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
|
|
|
|
if (!last)
|
|
return NULL;
|
|
|
|
return rb_entry(last, struct sched_entity, run_node);
|
|
}
|
|
|
|
/**************************************************************
|
|
* Scheduling class statistics methods:
|
|
*/
|
|
|
|
int sched_proc_update_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp,
|
|
loff_t *ppos)
|
|
{
|
|
int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
int factor = get_update_sysctl_factor();
|
|
|
|
if (ret || !write)
|
|
return ret;
|
|
|
|
sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
|
|
sysctl_sched_min_granularity);
|
|
|
|
#define WRT_SYSCTL(name) \
|
|
(normalized_sysctl_##name = sysctl_##name / (factor))
|
|
WRT_SYSCTL(sched_min_granularity);
|
|
WRT_SYSCTL(sched_latency);
|
|
WRT_SYSCTL(sched_wakeup_granularity);
|
|
#undef WRT_SYSCTL
|
|
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* delta /= w
|
|
*/
|
|
static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
|
|
{
|
|
if (unlikely(se->load.weight != NICE_0_LOAD))
|
|
delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
|
|
|
|
return delta;
|
|
}
|
|
|
|
/*
|
|
* The idea is to set a period in which each task runs once.
|
|
*
|
|
* When there are too many tasks (sched_nr_latency) we have to stretch
|
|
* this period because otherwise the slices get too small.
|
|
*
|
|
* p = (nr <= nl) ? l : l*nr/nl
|
|
*/
|
|
static u64 __sched_period(unsigned long nr_running)
|
|
{
|
|
u64 period = sysctl_sched_latency;
|
|
unsigned long nr_latency = sched_nr_latency;
|
|
|
|
if (unlikely(nr_running > nr_latency)) {
|
|
period = sysctl_sched_min_granularity;
|
|
period *= nr_running;
|
|
}
|
|
|
|
return period;
|
|
}
|
|
|
|
/*
|
|
* We calculate the wall-time slice from the period by taking a part
|
|
* proportional to the weight.
|
|
*
|
|
* s = p*P[w/rw]
|
|
*/
|
|
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
|
|
|
|
for_each_sched_entity(se) {
|
|
struct load_weight *load;
|
|
struct load_weight lw;
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
|
load = &cfs_rq->load;
|
|
|
|
if (unlikely(!se->on_rq)) {
|
|
lw = cfs_rq->load;
|
|
|
|
update_load_add(&lw, se->load.weight);
|
|
load = &lw;
|
|
}
|
|
slice = __calc_delta(slice, se->load.weight, load);
|
|
}
|
|
return slice;
|
|
}
|
|
|
|
/*
|
|
* We calculate the vruntime slice of a to-be-inserted task.
|
|
*
|
|
* vs = s/w
|
|
*/
|
|
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
return calc_delta_fair(sched_slice(cfs_rq, se), se);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
static unsigned long task_h_load(struct task_struct *p);
|
|
|
|
static inline void __update_task_entity_contrib(struct sched_entity *se);
|
|
|
|
/* Give new task start runnable values to heavy its load in infant time */
|
|
void init_task_runnable_average(struct task_struct *p)
|
|
{
|
|
u32 slice;
|
|
|
|
p->se.avg.decay_count = 0;
|
|
slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
|
|
p->se.avg.runnable_avg_sum = slice;
|
|
p->se.avg.runnable_avg_period = slice;
|
|
__update_task_entity_contrib(&p->se);
|
|
}
|
|
#else
|
|
void init_task_runnable_average(struct task_struct *p)
|
|
{
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Update the current task's runtime statistics.
|
|
*/
|
|
static void update_curr(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct sched_entity *curr = cfs_rq->curr;
|
|
u64 now = rq_clock_task(rq_of(cfs_rq));
|
|
u64 delta_exec;
|
|
|
|
if (unlikely(!curr))
|
|
return;
|
|
|
|
delta_exec = now - curr->exec_start;
|
|
if (unlikely((s64)delta_exec <= 0))
|
|
return;
|
|
|
|
curr->exec_start = now;
|
|
|
|
schedstat_set(curr->statistics.exec_max,
|
|
max(delta_exec, curr->statistics.exec_max));
|
|
|
|
curr->sum_exec_runtime += delta_exec;
|
|
schedstat_add(cfs_rq, exec_clock, delta_exec);
|
|
|
|
curr->vruntime += calc_delta_fair(delta_exec, curr);
|
|
update_min_vruntime(cfs_rq);
|
|
|
|
if (entity_is_task(curr)) {
|
|
struct task_struct *curtask = task_of(curr);
|
|
|
|
trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
|
|
cpuacct_charge(curtask, delta_exec);
|
|
account_group_exec_runtime(curtask, delta_exec);
|
|
}
|
|
|
|
account_cfs_rq_runtime(cfs_rq, delta_exec);
|
|
}
|
|
|
|
static inline void
|
|
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
|
|
}
|
|
|
|
/*
|
|
* Task is being enqueued - update stats:
|
|
*/
|
|
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/*
|
|
* Are we enqueueing a waiting task? (for current tasks
|
|
* a dequeue/enqueue event is a NOP)
|
|
*/
|
|
if (se != cfs_rq->curr)
|
|
update_stats_wait_start(cfs_rq, se);
|
|
}
|
|
|
|
static void
|
|
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
|
|
rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
|
|
schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
|
|
schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
|
|
rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
if (entity_is_task(se)) {
|
|
trace_sched_stat_wait(task_of(se),
|
|
rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
|
|
}
|
|
#endif
|
|
schedstat_set(se->statistics.wait_start, 0);
|
|
}
|
|
|
|
static inline void
|
|
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/*
|
|
* Mark the end of the wait period if dequeueing a
|
|
* waiting task:
|
|
*/
|
|
if (se != cfs_rq->curr)
|
|
update_stats_wait_end(cfs_rq, se);
|
|
}
|
|
|
|
/*
|
|
* We are picking a new current task - update its stats:
|
|
*/
|
|
static inline void
|
|
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/*
|
|
* We are starting a new run period:
|
|
*/
|
|
se->exec_start = rq_clock_task(rq_of(cfs_rq));
|
|
}
|
|
|
|
/**************************************************
|
|
* Scheduling class queueing methods:
|
|
*/
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
/*
|
|
* Approximate time to scan a full NUMA task in ms. The task scan period is
|
|
* calculated based on the tasks virtual memory size and
|
|
* numa_balancing_scan_size.
|
|
*/
|
|
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
|
|
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
|
|
|
|
/* Portion of address space to scan in MB */
|
|
unsigned int sysctl_numa_balancing_scan_size = 256;
|
|
|
|
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
|
|
unsigned int sysctl_numa_balancing_scan_delay = 1000;
|
|
|
|
/*
|
|
* After skipping a page migration on a shared page, skip N more numa page
|
|
* migrations unconditionally. This reduces the number of NUMA migrations
|
|
* in shared memory workloads, and has the effect of pulling tasks towards
|
|
* where their memory lives, over pulling the memory towards the task.
|
|
*/
|
|
unsigned int sysctl_numa_balancing_migrate_deferred = 16;
|
|
|
|
static unsigned int task_nr_scan_windows(struct task_struct *p)
|
|
{
|
|
unsigned long rss = 0;
|
|
unsigned long nr_scan_pages;
|
|
|
|
/*
|
|
* Calculations based on RSS as non-present and empty pages are skipped
|
|
* by the PTE scanner and NUMA hinting faults should be trapped based
|
|
* on resident pages
|
|
*/
|
|
nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
|
|
rss = get_mm_rss(p->mm);
|
|
if (!rss)
|
|
rss = nr_scan_pages;
|
|
|
|
rss = round_up(rss, nr_scan_pages);
|
|
return rss / nr_scan_pages;
|
|
}
|
|
|
|
/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
|
|
#define MAX_SCAN_WINDOW 2560
|
|
|
|
static unsigned int task_scan_min(struct task_struct *p)
|
|
{
|
|
unsigned int scan, floor;
|
|
unsigned int windows = 1;
|
|
|
|
if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
|
|
windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
|
|
floor = 1000 / windows;
|
|
|
|
scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
|
|
return max_t(unsigned int, floor, scan);
|
|
}
|
|
|
|
static unsigned int task_scan_max(struct task_struct *p)
|
|
{
|
|
unsigned int smin = task_scan_min(p);
|
|
unsigned int smax;
|
|
|
|
/* Watch for min being lower than max due to floor calculations */
|
|
smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
|
|
return max(smin, smax);
|
|
}
|
|
|
|
/*
|
|
* Once a preferred node is selected the scheduler balancer will prefer moving
|
|
* a task to that node for sysctl_numa_balancing_settle_count number of PTE
|
|
* scans. This will give the process the chance to accumulate more faults on
|
|
* the preferred node but still allow the scheduler to move the task again if
|
|
* the nodes CPUs are overloaded.
|
|
*/
|
|
unsigned int sysctl_numa_balancing_settle_count __read_mostly = 4;
|
|
|
|
static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
|
|
{
|
|
rq->nr_numa_running += (p->numa_preferred_nid != -1);
|
|
rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
|
|
}
|
|
|
|
static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
|
|
{
|
|
rq->nr_numa_running -= (p->numa_preferred_nid != -1);
|
|
rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
|
|
}
|
|
|
|
struct numa_group {
|
|
atomic_t refcount;
|
|
|
|
spinlock_t lock; /* nr_tasks, tasks */
|
|
int nr_tasks;
|
|
pid_t gid;
|
|
struct list_head task_list;
|
|
|
|
struct rcu_head rcu;
|
|
unsigned long total_faults;
|
|
unsigned long faults[0];
|
|
};
|
|
|
|
pid_t task_numa_group_id(struct task_struct *p)
|
|
{
|
|
return p->numa_group ? p->numa_group->gid : 0;
|
|
}
|
|
|
|
static inline int task_faults_idx(int nid, int priv)
|
|
{
|
|
return 2 * nid + priv;
|
|
}
|
|
|
|
static inline unsigned long task_faults(struct task_struct *p, int nid)
|
|
{
|
|
if (!p->numa_faults)
|
|
return 0;
|
|
|
|
return p->numa_faults[task_faults_idx(nid, 0)] +
|
|
p->numa_faults[task_faults_idx(nid, 1)];
|
|
}
|
|
|
|
static inline unsigned long group_faults(struct task_struct *p, int nid)
|
|
{
|
|
if (!p->numa_group)
|
|
return 0;
|
|
|
|
return p->numa_group->faults[2*nid] + p->numa_group->faults[2*nid+1];
|
|
}
|
|
|
|
/*
|
|
* These return the fraction of accesses done by a particular task, or
|
|
* task group, on a particular numa node. The group weight is given a
|
|
* larger multiplier, in order to group tasks together that are almost
|
|
* evenly spread out between numa nodes.
|
|
*/
|
|
static inline unsigned long task_weight(struct task_struct *p, int nid)
|
|
{
|
|
unsigned long total_faults;
|
|
|
|
if (!p->numa_faults)
|
|
return 0;
|
|
|
|
total_faults = p->total_numa_faults;
|
|
|
|
if (!total_faults)
|
|
return 0;
|
|
|
|
return 1000 * task_faults(p, nid) / total_faults;
|
|
}
|
|
|
|
static inline unsigned long group_weight(struct task_struct *p, int nid)
|
|
{
|
|
if (!p->numa_group || !p->numa_group->total_faults)
|
|
return 0;
|
|
|
|
return 1000 * group_faults(p, nid) / p->numa_group->total_faults;
|
|
}
|
|
|
|
static unsigned long weighted_cpuload(const int cpu);
|
|
static unsigned long source_load(int cpu, int type);
|
|
static unsigned long target_load(int cpu, int type);
|
|
static unsigned long power_of(int cpu);
|
|
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
|
|
|
|
/* Cached statistics for all CPUs within a node */
|
|
struct numa_stats {
|
|
unsigned long nr_running;
|
|
unsigned long load;
|
|
|
|
/* Total compute capacity of CPUs on a node */
|
|
unsigned long power;
|
|
|
|
/* Approximate capacity in terms of runnable tasks on a node */
|
|
unsigned long capacity;
|
|
int has_capacity;
|
|
};
|
|
|
|
/*
|
|
* XXX borrowed from update_sg_lb_stats
|
|
*/
|
|
static void update_numa_stats(struct numa_stats *ns, int nid)
|
|
{
|
|
int cpu, cpus = 0;
|
|
|
|
memset(ns, 0, sizeof(*ns));
|
|
for_each_cpu(cpu, cpumask_of_node(nid)) {
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
ns->nr_running += rq->nr_running;
|
|
ns->load += weighted_cpuload(cpu);
|
|
ns->power += power_of(cpu);
|
|
|
|
cpus++;
|
|
}
|
|
|
|
/*
|
|
* If we raced with hotplug and there are no CPUs left in our mask
|
|
* the @ns structure is NULL'ed and task_numa_compare() will
|
|
* not find this node attractive.
|
|
*
|
|
* We'll either bail at !has_capacity, or we'll detect a huge imbalance
|
|
* and bail there.
|
|
*/
|
|
if (!cpus)
|
|
return;
|
|
|
|
ns->load = (ns->load * SCHED_POWER_SCALE) / ns->power;
|
|
ns->capacity = DIV_ROUND_CLOSEST(ns->power, SCHED_POWER_SCALE);
|
|
ns->has_capacity = (ns->nr_running < ns->capacity);
|
|
}
|
|
|
|
struct task_numa_env {
|
|
struct task_struct *p;
|
|
|
|
int src_cpu, src_nid;
|
|
int dst_cpu, dst_nid;
|
|
|
|
struct numa_stats src_stats, dst_stats;
|
|
|
|
int imbalance_pct, idx;
|
|
|
|
struct task_struct *best_task;
|
|
long best_imp;
|
|
int best_cpu;
|
|
};
|
|
|
|
static void task_numa_assign(struct task_numa_env *env,
|
|
struct task_struct *p, long imp)
|
|
{
|
|
if (env->best_task)
|
|
put_task_struct(env->best_task);
|
|
if (p)
|
|
get_task_struct(p);
|
|
|
|
env->best_task = p;
|
|
env->best_imp = imp;
|
|
env->best_cpu = env->dst_cpu;
|
|
}
|
|
|
|
/*
|
|
* This checks if the overall compute and NUMA accesses of the system would
|
|
* be improved if the source tasks was migrated to the target dst_cpu taking
|
|
* into account that it might be best if task running on the dst_cpu should
|
|
* be exchanged with the source task
|
|
*/
|
|
static void task_numa_compare(struct task_numa_env *env,
|
|
long taskimp, long groupimp)
|
|
{
|
|
struct rq *src_rq = cpu_rq(env->src_cpu);
|
|
struct rq *dst_rq = cpu_rq(env->dst_cpu);
|
|
struct task_struct *cur;
|
|
long dst_load, src_load;
|
|
long load;
|
|
long imp = (groupimp > 0) ? groupimp : taskimp;
|
|
|
|
rcu_read_lock();
|
|
cur = ACCESS_ONCE(dst_rq->curr);
|
|
if (cur->pid == 0) /* idle */
|
|
cur = NULL;
|
|
|
|
/*
|
|
* "imp" is the fault differential for the source task between the
|
|
* source and destination node. Calculate the total differential for
|
|
* the source task and potential destination task. The more negative
|
|
* the value is, the more rmeote accesses that would be expected to
|
|
* be incurred if the tasks were swapped.
|
|
*/
|
|
if (cur) {
|
|
/* Skip this swap candidate if cannot move to the source cpu */
|
|
if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
|
|
goto unlock;
|
|
|
|
/*
|
|
* If dst and source tasks are in the same NUMA group, or not
|
|
* in any group then look only at task weights.
|
|
*/
|
|
if (cur->numa_group == env->p->numa_group) {
|
|
imp = taskimp + task_weight(cur, env->src_nid) -
|
|
task_weight(cur, env->dst_nid);
|
|
/*
|
|
* Add some hysteresis to prevent swapping the
|
|
* tasks within a group over tiny differences.
|
|
*/
|
|
if (cur->numa_group)
|
|
imp -= imp/16;
|
|
} else {
|
|
/*
|
|
* Compare the group weights. If a task is all by
|
|
* itself (not part of a group), use the task weight
|
|
* instead.
|
|
*/
|
|
if (env->p->numa_group)
|
|
imp = groupimp;
|
|
else
|
|
imp = taskimp;
|
|
|
|
if (cur->numa_group)
|
|
imp += group_weight(cur, env->src_nid) -
|
|
group_weight(cur, env->dst_nid);
|
|
else
|
|
imp += task_weight(cur, env->src_nid) -
|
|
task_weight(cur, env->dst_nid);
|
|
}
|
|
}
|
|
|
|
if (imp < env->best_imp)
|
|
goto unlock;
|
|
|
|
if (!cur) {
|
|
/* Is there capacity at our destination? */
|
|
if (env->src_stats.has_capacity &&
|
|
!env->dst_stats.has_capacity)
|
|
goto unlock;
|
|
|
|
goto balance;
|
|
}
|
|
|
|
/* Balance doesn't matter much if we're running a task per cpu */
|
|
if (src_rq->nr_running == 1 && dst_rq->nr_running == 1)
|
|
goto assign;
|
|
|
|
/*
|
|
* In the overloaded case, try and keep the load balanced.
|
|
*/
|
|
balance:
|
|
dst_load = env->dst_stats.load;
|
|
src_load = env->src_stats.load;
|
|
|
|
/* XXX missing power terms */
|
|
load = task_h_load(env->p);
|
|
dst_load += load;
|
|
src_load -= load;
|
|
|
|
if (cur) {
|
|
load = task_h_load(cur);
|
|
dst_load -= load;
|
|
src_load += load;
|
|
}
|
|
|
|
/* make src_load the smaller */
|
|
if (dst_load < src_load)
|
|
swap(dst_load, src_load);
|
|
|
|
if (src_load * env->imbalance_pct < dst_load * 100)
|
|
goto unlock;
|
|
|
|
assign:
|
|
task_numa_assign(env, cur, imp);
|
|
unlock:
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
static void task_numa_find_cpu(struct task_numa_env *env,
|
|
long taskimp, long groupimp)
|
|
{
|
|
int cpu;
|
|
|
|
for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
|
|
/* Skip this CPU if the source task cannot migrate */
|
|
if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
|
|
continue;
|
|
|
|
env->dst_cpu = cpu;
|
|
task_numa_compare(env, taskimp, groupimp);
|
|
}
|
|
}
|
|
|
|
static int task_numa_migrate(struct task_struct *p)
|
|
{
|
|
struct task_numa_env env = {
|
|
.p = p,
|
|
|
|
.src_cpu = task_cpu(p),
|
|
.src_nid = task_node(p),
|
|
|
|
.imbalance_pct = 112,
|
|
|
|
.best_task = NULL,
|
|
.best_imp = 0,
|
|
.best_cpu = -1
|
|
};
|
|
struct sched_domain *sd;
|
|
unsigned long taskweight, groupweight;
|
|
int nid, ret;
|
|
long taskimp, groupimp;
|
|
|
|
/*
|
|
* Pick the lowest SD_NUMA domain, as that would have the smallest
|
|
* imbalance and would be the first to start moving tasks about.
|
|
*
|
|
* And we want to avoid any moving of tasks about, as that would create
|
|
* random movement of tasks -- counter the numa conditions we're trying
|
|
* to satisfy here.
|
|
*/
|
|
rcu_read_lock();
|
|
sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
|
|
if (sd)
|
|
env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* Cpusets can break the scheduler domain tree into smaller
|
|
* balance domains, some of which do not cross NUMA boundaries.
|
|
* Tasks that are "trapped" in such domains cannot be migrated
|
|
* elsewhere, so there is no point in (re)trying.
|
|
*/
|
|
if (unlikely(!sd)) {
|
|
p->numa_preferred_nid = cpu_to_node(task_cpu(p));
|
|
return -EINVAL;
|
|
}
|
|
|
|
taskweight = task_weight(p, env.src_nid);
|
|
groupweight = group_weight(p, env.src_nid);
|
|
update_numa_stats(&env.src_stats, env.src_nid);
|
|
env.dst_nid = p->numa_preferred_nid;
|
|
taskimp = task_weight(p, env.dst_nid) - taskweight;
|
|
groupimp = group_weight(p, env.dst_nid) - groupweight;
|
|
update_numa_stats(&env.dst_stats, env.dst_nid);
|
|
|
|
/* If the preferred nid has capacity, try to use it. */
|
|
if (env.dst_stats.has_capacity)
|
|
task_numa_find_cpu(&env, taskimp, groupimp);
|
|
|
|
/* No space available on the preferred nid. Look elsewhere. */
|
|
if (env.best_cpu == -1) {
|
|
for_each_online_node(nid) {
|
|
if (nid == env.src_nid || nid == p->numa_preferred_nid)
|
|
continue;
|
|
|
|
/* Only consider nodes where both task and groups benefit */
|
|
taskimp = task_weight(p, nid) - taskweight;
|
|
groupimp = group_weight(p, nid) - groupweight;
|
|
if (taskimp < 0 && groupimp < 0)
|
|
continue;
|
|
|
|
env.dst_nid = nid;
|
|
update_numa_stats(&env.dst_stats, env.dst_nid);
|
|
task_numa_find_cpu(&env, taskimp, groupimp);
|
|
}
|
|
}
|
|
|
|
/* No better CPU than the current one was found. */
|
|
if (env.best_cpu == -1)
|
|
return -EAGAIN;
|
|
|
|
sched_setnuma(p, env.dst_nid);
|
|
|
|
/*
|
|
* Reset the scan period if the task is being rescheduled on an
|
|
* alternative node to recheck if the tasks is now properly placed.
|
|
*/
|
|
p->numa_scan_period = task_scan_min(p);
|
|
|
|
if (env.best_task == NULL) {
|
|
int ret = migrate_task_to(p, env.best_cpu);
|
|
return ret;
|
|
}
|
|
|
|
ret = migrate_swap(p, env.best_task);
|
|
put_task_struct(env.best_task);
|
|
return ret;
|
|
}
|
|
|
|
/* Attempt to migrate a task to a CPU on the preferred node. */
|
|
static void numa_migrate_preferred(struct task_struct *p)
|
|
{
|
|
/* This task has no NUMA fault statistics yet */
|
|
if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
|
|
return;
|
|
|
|
/* Periodically retry migrating the task to the preferred node */
|
|
p->numa_migrate_retry = jiffies + HZ;
|
|
|
|
/* Success if task is already running on preferred CPU */
|
|
if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid)
|
|
return;
|
|
|
|
/* Otherwise, try migrate to a CPU on the preferred node */
|
|
task_numa_migrate(p);
|
|
}
|
|
|
|
/*
|
|
* When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
|
|
* increments. The more local the fault statistics are, the higher the scan
|
|
* period will be for the next scan window. If local/remote ratio is below
|
|
* NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the
|
|
* scan period will decrease
|
|
*/
|
|
#define NUMA_PERIOD_SLOTS 10
|
|
#define NUMA_PERIOD_THRESHOLD 3
|
|
|
|
/*
|
|
* Increase the scan period (slow down scanning) if the majority of
|
|
* our memory is already on our local node, or if the majority of
|
|
* the page accesses are shared with other processes.
|
|
* Otherwise, decrease the scan period.
|
|
*/
|
|
static void update_task_scan_period(struct task_struct *p,
|
|
unsigned long shared, unsigned long private)
|
|
{
|
|
unsigned int period_slot;
|
|
int ratio;
|
|
int diff;
|
|
|
|
unsigned long remote = p->numa_faults_locality[0];
|
|
unsigned long local = p->numa_faults_locality[1];
|
|
|
|
/*
|
|
* If there were no record hinting faults then either the task is
|
|
* completely idle or all activity is areas that are not of interest
|
|
* to automatic numa balancing. Scan slower
|
|
*/
|
|
if (local + shared == 0) {
|
|
p->numa_scan_period = min(p->numa_scan_period_max,
|
|
p->numa_scan_period << 1);
|
|
|
|
p->mm->numa_next_scan = jiffies +
|
|
msecs_to_jiffies(p->numa_scan_period);
|
|
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Prepare to scale scan period relative to the current period.
|
|
* == NUMA_PERIOD_THRESHOLD scan period stays the same
|
|
* < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
|
|
* >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
|
|
*/
|
|
period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
|
|
ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
|
|
if (ratio >= NUMA_PERIOD_THRESHOLD) {
|
|
int slot = ratio - NUMA_PERIOD_THRESHOLD;
|
|
if (!slot)
|
|
slot = 1;
|
|
diff = slot * period_slot;
|
|
} else {
|
|
diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
|
|
|
|
/*
|
|
* Scale scan rate increases based on sharing. There is an
|
|
* inverse relationship between the degree of sharing and
|
|
* the adjustment made to the scanning period. Broadly
|
|
* speaking the intent is that there is little point
|
|
* scanning faster if shared accesses dominate as it may
|
|
* simply bounce migrations uselessly
|
|
*/
|
|
period_slot = DIV_ROUND_UP(diff, NUMA_PERIOD_SLOTS);
|
|
ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared));
|
|
diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
|
|
}
|
|
|
|
p->numa_scan_period = clamp(p->numa_scan_period + diff,
|
|
task_scan_min(p), task_scan_max(p));
|
|
memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
|
|
}
|
|
|
|
static void task_numa_placement(struct task_struct *p)
|
|
{
|
|
int seq, nid, max_nid = -1, max_group_nid = -1;
|
|
unsigned long max_faults = 0, max_group_faults = 0;
|
|
unsigned long fault_types[2] = { 0, 0 };
|
|
spinlock_t *group_lock = NULL;
|
|
|
|
seq = ACCESS_ONCE(p->mm->numa_scan_seq);
|
|
if (p->numa_scan_seq == seq)
|
|
return;
|
|
p->numa_scan_seq = seq;
|
|
p->numa_scan_period_max = task_scan_max(p);
|
|
|
|
/* If the task is part of a group prevent parallel updates to group stats */
|
|
if (p->numa_group) {
|
|
group_lock = &p->numa_group->lock;
|
|
spin_lock(group_lock);
|
|
}
|
|
|
|
/* Find the node with the highest number of faults */
|
|
for_each_online_node(nid) {
|
|
unsigned long faults = 0, group_faults = 0;
|
|
int priv, i;
|
|
|
|
for (priv = 0; priv < 2; priv++) {
|
|
long diff;
|
|
|
|
i = task_faults_idx(nid, priv);
|
|
diff = -p->numa_faults[i];
|
|
|
|
/* Decay existing window, copy faults since last scan */
|
|
p->numa_faults[i] >>= 1;
|
|
p->numa_faults[i] += p->numa_faults_buffer[i];
|
|
fault_types[priv] += p->numa_faults_buffer[i];
|
|
p->numa_faults_buffer[i] = 0;
|
|
|
|
faults += p->numa_faults[i];
|
|
diff += p->numa_faults[i];
|
|
p->total_numa_faults += diff;
|
|
if (p->numa_group) {
|
|
/* safe because we can only change our own group */
|
|
p->numa_group->faults[i] += diff;
|
|
p->numa_group->total_faults += diff;
|
|
group_faults += p->numa_group->faults[i];
|
|
}
|
|
}
|
|
|
|
if (faults > max_faults) {
|
|
max_faults = faults;
|
|
max_nid = nid;
|
|
}
|
|
|
|
if (group_faults > max_group_faults) {
|
|
max_group_faults = group_faults;
|
|
max_group_nid = nid;
|
|
}
|
|
}
|
|
|
|
update_task_scan_period(p, fault_types[0], fault_types[1]);
|
|
|
|
if (p->numa_group) {
|
|
/*
|
|
* If the preferred task and group nids are different,
|
|
* iterate over the nodes again to find the best place.
|
|
*/
|
|
if (max_nid != max_group_nid) {
|
|
unsigned long weight, max_weight = 0;
|
|
|
|
for_each_online_node(nid) {
|
|
weight = task_weight(p, nid) + group_weight(p, nid);
|
|
if (weight > max_weight) {
|
|
max_weight = weight;
|
|
max_nid = nid;
|
|
}
|
|
}
|
|
}
|
|
|
|
spin_unlock(group_lock);
|
|
}
|
|
|
|
/* Preferred node as the node with the most faults */
|
|
if (max_faults && max_nid != p->numa_preferred_nid) {
|
|
/* Update the preferred nid and migrate task if possible */
|
|
sched_setnuma(p, max_nid);
|
|
numa_migrate_preferred(p);
|
|
}
|
|
}
|
|
|
|
static inline int get_numa_group(struct numa_group *grp)
|
|
{
|
|
return atomic_inc_not_zero(&grp->refcount);
|
|
}
|
|
|
|
static inline void put_numa_group(struct numa_group *grp)
|
|
{
|
|
if (atomic_dec_and_test(&grp->refcount))
|
|
kfree_rcu(grp, rcu);
|
|
}
|
|
|
|
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
|
|
int *priv)
|
|
{
|
|
struct numa_group *grp, *my_grp;
|
|
struct task_struct *tsk;
|
|
bool join = false;
|
|
int cpu = cpupid_to_cpu(cpupid);
|
|
int i;
|
|
|
|
if (unlikely(!p->numa_group)) {
|
|
unsigned int size = sizeof(struct numa_group) +
|
|
2*nr_node_ids*sizeof(unsigned long);
|
|
|
|
grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
|
|
if (!grp)
|
|
return;
|
|
|
|
atomic_set(&grp->refcount, 1);
|
|
spin_lock_init(&grp->lock);
|
|
INIT_LIST_HEAD(&grp->task_list);
|
|
grp->gid = p->pid;
|
|
|
|
for (i = 0; i < 2*nr_node_ids; i++)
|
|
grp->faults[i] = p->numa_faults[i];
|
|
|
|
grp->total_faults = p->total_numa_faults;
|
|
|
|
list_add(&p->numa_entry, &grp->task_list);
|
|
grp->nr_tasks++;
|
|
rcu_assign_pointer(p->numa_group, grp);
|
|
}
|
|
|
|
rcu_read_lock();
|
|
tsk = ACCESS_ONCE(cpu_rq(cpu)->curr);
|
|
|
|
if (!cpupid_match_pid(tsk, cpupid))
|
|
goto no_join;
|
|
|
|
grp = rcu_dereference(tsk->numa_group);
|
|
if (!grp)
|
|
goto no_join;
|
|
|
|
my_grp = p->numa_group;
|
|
if (grp == my_grp)
|
|
goto no_join;
|
|
|
|
/*
|
|
* Only join the other group if its bigger; if we're the bigger group,
|
|
* the other task will join us.
|
|
*/
|
|
if (my_grp->nr_tasks > grp->nr_tasks)
|
|
goto no_join;
|
|
|
|
/*
|
|
* Tie-break on the grp address.
|
|
*/
|
|
if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
|
|
goto no_join;
|
|
|
|
/* Always join threads in the same process. */
|
|
if (tsk->mm == current->mm)
|
|
join = true;
|
|
|
|
/* Simple filter to avoid false positives due to PID collisions */
|
|
if (flags & TNF_SHARED)
|
|
join = true;
|
|
|
|
/* Update priv based on whether false sharing was detected */
|
|
*priv = !join;
|
|
|
|
if (join && !get_numa_group(grp))
|
|
goto no_join;
|
|
|
|
rcu_read_unlock();
|
|
|
|
if (!join)
|
|
return;
|
|
|
|
double_lock(&my_grp->lock, &grp->lock);
|
|
|
|
for (i = 0; i < 2*nr_node_ids; i++) {
|
|
my_grp->faults[i] -= p->numa_faults[i];
|
|
grp->faults[i] += p->numa_faults[i];
|
|
}
|
|
my_grp->total_faults -= p->total_numa_faults;
|
|
grp->total_faults += p->total_numa_faults;
|
|
|
|
list_move(&p->numa_entry, &grp->task_list);
|
|
my_grp->nr_tasks--;
|
|
grp->nr_tasks++;
|
|
|
|
spin_unlock(&my_grp->lock);
|
|
spin_unlock(&grp->lock);
|
|
|
|
rcu_assign_pointer(p->numa_group, grp);
|
|
|
|
put_numa_group(my_grp);
|
|
return;
|
|
|
|
no_join:
|
|
rcu_read_unlock();
|
|
return;
|
|
}
|
|
|
|
void task_numa_free(struct task_struct *p)
|
|
{
|
|
struct numa_group *grp = p->numa_group;
|
|
int i;
|
|
void *numa_faults = p->numa_faults;
|
|
|
|
if (grp) {
|
|
spin_lock(&grp->lock);
|
|
for (i = 0; i < 2*nr_node_ids; i++)
|
|
grp->faults[i] -= p->numa_faults[i];
|
|
grp->total_faults -= p->total_numa_faults;
|
|
|
|
list_del(&p->numa_entry);
|
|
grp->nr_tasks--;
|
|
spin_unlock(&grp->lock);
|
|
rcu_assign_pointer(p->numa_group, NULL);
|
|
put_numa_group(grp);
|
|
}
|
|
|
|
p->numa_faults = NULL;
|
|
p->numa_faults_buffer = NULL;
|
|
kfree(numa_faults);
|
|
}
|
|
|
|
/*
|
|
* Got a PROT_NONE fault for a page on @node.
|
|
*/
|
|
void task_numa_fault(int last_cpupid, int node, int pages, int flags)
|
|
{
|
|
struct task_struct *p = current;
|
|
bool migrated = flags & TNF_MIGRATED;
|
|
int priv;
|
|
|
|
if (!numabalancing_enabled)
|
|
return;
|
|
|
|
/* for example, ksmd faulting in a user's mm */
|
|
if (!p->mm)
|
|
return;
|
|
|
|
/* Do not worry about placement if exiting */
|
|
if (p->state == TASK_DEAD)
|
|
return;
|
|
|
|
/* Allocate buffer to track faults on a per-node basis */
|
|
if (unlikely(!p->numa_faults)) {
|
|
int size = sizeof(*p->numa_faults) * 2 * nr_node_ids;
|
|
|
|
/* numa_faults and numa_faults_buffer share the allocation */
|
|
p->numa_faults = kzalloc(size * 2, GFP_KERNEL|__GFP_NOWARN);
|
|
if (!p->numa_faults)
|
|
return;
|
|
|
|
BUG_ON(p->numa_faults_buffer);
|
|
p->numa_faults_buffer = p->numa_faults + (2 * nr_node_ids);
|
|
p->total_numa_faults = 0;
|
|
memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
|
|
}
|
|
|
|
/*
|
|
* First accesses are treated as private, otherwise consider accesses
|
|
* to be private if the accessing pid has not changed
|
|
*/
|
|
if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
|
|
priv = 1;
|
|
} else {
|
|
priv = cpupid_match_pid(p, last_cpupid);
|
|
if (!priv && !(flags & TNF_NO_GROUP))
|
|
task_numa_group(p, last_cpupid, flags, &priv);
|
|
}
|
|
|
|
task_numa_placement(p);
|
|
|
|
/*
|
|
* Retry task to preferred node migration periodically, in case it
|
|
* case it previously failed, or the scheduler moved us.
|
|
*/
|
|
if (time_after(jiffies, p->numa_migrate_retry))
|
|
numa_migrate_preferred(p);
|
|
|
|
if (migrated)
|
|
p->numa_pages_migrated += pages;
|
|
|
|
p->numa_faults_buffer[task_faults_idx(node, priv)] += pages;
|
|
p->numa_faults_locality[!!(flags & TNF_FAULT_LOCAL)] += pages;
|
|
}
|
|
|
|
static void reset_ptenuma_scan(struct task_struct *p)
|
|
{
|
|
ACCESS_ONCE(p->mm->numa_scan_seq)++;
|
|
p->mm->numa_scan_offset = 0;
|
|
}
|
|
|
|
/*
|
|
* The expensive part of numa migration is done from task_work context.
|
|
* Triggered from task_tick_numa().
|
|
*/
|
|
void task_numa_work(struct callback_head *work)
|
|
{
|
|
unsigned long migrate, next_scan, now = jiffies;
|
|
struct task_struct *p = current;
|
|
struct mm_struct *mm = p->mm;
|
|
struct vm_area_struct *vma;
|
|
unsigned long start, end;
|
|
unsigned long nr_pte_updates = 0;
|
|
long pages;
|
|
|
|
WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
|
|
|
|
work->next = work; /* protect against double add */
|
|
/*
|
|
* Who cares about NUMA placement when they're dying.
|
|
*
|
|
* NOTE: make sure not to dereference p->mm before this check,
|
|
* exit_task_work() happens _after_ exit_mm() so we could be called
|
|
* without p->mm even though we still had it when we enqueued this
|
|
* work.
|
|
*/
|
|
if (p->flags & PF_EXITING)
|
|
return;
|
|
|
|
if (!mm->numa_next_scan) {
|
|
mm->numa_next_scan = now +
|
|
msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
|
|
}
|
|
|
|
/*
|
|
* Enforce maximal scan/migration frequency..
|
|
*/
|
|
migrate = mm->numa_next_scan;
|
|
if (time_before(now, migrate))
|
|
return;
|
|
|
|
if (p->numa_scan_period == 0) {
|
|
p->numa_scan_period_max = task_scan_max(p);
|
|
p->numa_scan_period = task_scan_min(p);
|
|
}
|
|
|
|
next_scan = now + msecs_to_jiffies(p->numa_scan_period);
|
|
if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
|
|
return;
|
|
|
|
/*
|
|
* Delay this task enough that another task of this mm will likely win
|
|
* the next time around.
|
|
*/
|
|
p->node_stamp += 2 * TICK_NSEC;
|
|
|
|
start = mm->numa_scan_offset;
|
|
pages = sysctl_numa_balancing_scan_size;
|
|
pages <<= 20 - PAGE_SHIFT; /* MB in pages */
|
|
if (!pages)
|
|
return;
|
|
|
|
down_read(&mm->mmap_sem);
|
|
vma = find_vma(mm, start);
|
|
if (!vma) {
|
|
reset_ptenuma_scan(p);
|
|
start = 0;
|
|
vma = mm->mmap;
|
|
}
|
|
for (; vma; vma = vma->vm_next) {
|
|
if (!vma_migratable(vma) || !vma_policy_mof(p, vma))
|
|
continue;
|
|
|
|
/*
|
|
* Shared library pages mapped by multiple processes are not
|
|
* migrated as it is expected they are cache replicated. Avoid
|
|
* hinting faults in read-only file-backed mappings or the vdso
|
|
* as migrating the pages will be of marginal benefit.
|
|
*/
|
|
if (!vma->vm_mm ||
|
|
(vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
|
|
continue;
|
|
|
|
/*
|
|
* Skip inaccessible VMAs to avoid any confusion between
|
|
* PROT_NONE and NUMA hinting ptes
|
|
*/
|
|
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
|
|
continue;
|
|
|
|
do {
|
|
start = max(start, vma->vm_start);
|
|
end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
|
|
end = min(end, vma->vm_end);
|
|
nr_pte_updates += change_prot_numa(vma, start, end);
|
|
|
|
/*
|
|
* Scan sysctl_numa_balancing_scan_size but ensure that
|
|
* at least one PTE is updated so that unused virtual
|
|
* address space is quickly skipped.
|
|
*/
|
|
if (nr_pte_updates)
|
|
pages -= (end - start) >> PAGE_SHIFT;
|
|
|
|
start = end;
|
|
if (pages <= 0)
|
|
goto out;
|
|
} while (end != vma->vm_end);
|
|
}
|
|
|
|
out:
|
|
/*
|
|
* It is possible to reach the end of the VMA list but the last few
|
|
* VMAs are not guaranteed to the vma_migratable. If they are not, we
|
|
* would find the !migratable VMA on the next scan but not reset the
|
|
* scanner to the start so check it now.
|
|
*/
|
|
if (vma)
|
|
mm->numa_scan_offset = start;
|
|
else
|
|
reset_ptenuma_scan(p);
|
|
up_read(&mm->mmap_sem);
|
|
}
|
|
|
|
/*
|
|
* Drive the periodic memory faults..
|
|
*/
|
|
void task_tick_numa(struct rq *rq, struct task_struct *curr)
|
|
{
|
|
struct callback_head *work = &curr->numa_work;
|
|
u64 period, now;
|
|
|
|
/*
|
|
* We don't care about NUMA placement if we don't have memory.
|
|
*/
|
|
if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
|
|
return;
|
|
|
|
/*
|
|
* Using runtime rather than walltime has the dual advantage that
|
|
* we (mostly) drive the selection from busy threads and that the
|
|
* task needs to have done some actual work before we bother with
|
|
* NUMA placement.
|
|
*/
|
|
now = curr->se.sum_exec_runtime;
|
|
period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
|
|
|
|
if (now - curr->node_stamp > period) {
|
|
if (!curr->node_stamp)
|
|
curr->numa_scan_period = task_scan_min(curr);
|
|
curr->node_stamp += period;
|
|
|
|
if (!time_before(jiffies, curr->mm->numa_next_scan)) {
|
|
init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
|
|
task_work_add(curr, work, true);
|
|
}
|
|
}
|
|
}
|
|
#else
|
|
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
|
|
{
|
|
}
|
|
|
|
static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
|
|
static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
#endif /* CONFIG_NUMA_BALANCING */
|
|
|
|
static void
|
|
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
update_load_add(&cfs_rq->load, se->load.weight);
|
|
if (!parent_entity(se))
|
|
update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
|
|
#ifdef CONFIG_SMP
|
|
if (entity_is_task(se)) {
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
|
|
account_numa_enqueue(rq, task_of(se));
|
|
list_add(&se->group_node, &rq->cfs_tasks);
|
|
}
|
|
#endif
|
|
cfs_rq->nr_running++;
|
|
}
|
|
|
|
static void
|
|
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
update_load_sub(&cfs_rq->load, se->load.weight);
|
|
if (!parent_entity(se))
|
|
update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
|
|
if (entity_is_task(se)) {
|
|
account_numa_dequeue(rq_of(cfs_rq), task_of(se));
|
|
list_del_init(&se->group_node);
|
|
}
|
|
cfs_rq->nr_running--;
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
# ifdef CONFIG_SMP
|
|
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
|
|
{
|
|
long tg_weight;
|
|
|
|
/*
|
|
* Use this CPU's actual weight instead of the last load_contribution
|
|
* to gain a more accurate current total weight. See
|
|
* update_cfs_rq_load_contribution().
|
|
*/
|
|
tg_weight = atomic_long_read(&tg->load_avg);
|
|
tg_weight -= cfs_rq->tg_load_contrib;
|
|
tg_weight += cfs_rq->load.weight;
|
|
|
|
return tg_weight;
|
|
}
|
|
|
|
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
|
|
{
|
|
long tg_weight, load, shares;
|
|
|
|
tg_weight = calc_tg_weight(tg, cfs_rq);
|
|
load = cfs_rq->load.weight;
|
|
|
|
shares = (tg->shares * load);
|
|
if (tg_weight)
|
|
shares /= tg_weight;
|
|
|
|
if (shares < MIN_SHARES)
|
|
shares = MIN_SHARES;
|
|
if (shares > tg->shares)
|
|
shares = tg->shares;
|
|
|
|
return shares;
|
|
}
|
|
# else /* CONFIG_SMP */
|
|
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
|
|
{
|
|
return tg->shares;
|
|
}
|
|
# endif /* CONFIG_SMP */
|
|
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
|
|
unsigned long weight)
|
|
{
|
|
if (se->on_rq) {
|
|
/* commit outstanding execution time */
|
|
if (cfs_rq->curr == se)
|
|
update_curr(cfs_rq);
|
|
account_entity_dequeue(cfs_rq, se);
|
|
}
|
|
|
|
update_load_set(&se->load, weight);
|
|
|
|
if (se->on_rq)
|
|
account_entity_enqueue(cfs_rq, se);
|
|
}
|
|
|
|
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
|
|
|
|
static void update_cfs_shares(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct task_group *tg;
|
|
struct sched_entity *se;
|
|
long shares;
|
|
|
|
tg = cfs_rq->tg;
|
|
se = tg->se[cpu_of(rq_of(cfs_rq))];
|
|
if (!se || throttled_hierarchy(cfs_rq))
|
|
return;
|
|
#ifndef CONFIG_SMP
|
|
if (likely(se->load.weight == tg->shares))
|
|
return;
|
|
#endif
|
|
shares = calc_cfs_shares(cfs_rq, tg);
|
|
|
|
reweight_entity(cfs_rq_of(se), se, shares);
|
|
}
|
|
#else /* CONFIG_FAIR_GROUP_SCHED */
|
|
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
|
|
{
|
|
}
|
|
#endif /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* We choose a half-life close to 1 scheduling period.
|
|
* Note: The tables below are dependent on this value.
|
|
*/
|
|
#define LOAD_AVG_PERIOD 32
|
|
#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
|
|
#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
|
|
|
|
/* Precomputed fixed inverse multiplies for multiplication by y^n */
|
|
static const u32 runnable_avg_yN_inv[] = {
|
|
0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
|
|
0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
|
|
0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
|
|
0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
|
|
0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
|
|
0x85aac367, 0x82cd8698,
|
|
};
|
|
|
|
/*
|
|
* Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
|
|
* over-estimates when re-combining.
|
|
*/
|
|
static const u32 runnable_avg_yN_sum[] = {
|
|
0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
|
|
9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
|
|
17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
|
|
};
|
|
|
|
/*
|
|
* Approximate:
|
|
* val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
|
|
*/
|
|
static __always_inline u64 decay_load(u64 val, u64 n)
|
|
{
|
|
unsigned int local_n;
|
|
|
|
if (!n)
|
|
return val;
|
|
else if (unlikely(n > LOAD_AVG_PERIOD * 63))
|
|
return 0;
|
|
|
|
/* after bounds checking we can collapse to 32-bit */
|
|
local_n = n;
|
|
|
|
/*
|
|
* As y^PERIOD = 1/2, we can combine
|
|
* y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
|
|
* With a look-up table which covers k^n (n<PERIOD)
|
|
*
|
|
* To achieve constant time decay_load.
|
|
*/
|
|
if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
|
|
val >>= local_n / LOAD_AVG_PERIOD;
|
|
local_n %= LOAD_AVG_PERIOD;
|
|
}
|
|
|
|
val *= runnable_avg_yN_inv[local_n];
|
|
/* We don't use SRR here since we always want to round down. */
|
|
return val >> 32;
|
|
}
|
|
|
|
/*
|
|
* For updates fully spanning n periods, the contribution to runnable
|
|
* average will be: \Sum 1024*y^n
|
|
*
|
|
* We can compute this reasonably efficiently by combining:
|
|
* y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
|
|
*/
|
|
static u32 __compute_runnable_contrib(u64 n)
|
|
{
|
|
u32 contrib = 0;
|
|
|
|
if (likely(n <= LOAD_AVG_PERIOD))
|
|
return runnable_avg_yN_sum[n];
|
|
else if (unlikely(n >= LOAD_AVG_MAX_N))
|
|
return LOAD_AVG_MAX;
|
|
|
|
/* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
|
|
do {
|
|
contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
|
|
contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
|
|
|
|
n -= LOAD_AVG_PERIOD;
|
|
} while (n > LOAD_AVG_PERIOD);
|
|
|
|
contrib = decay_load(contrib, n);
|
|
return contrib + runnable_avg_yN_sum[n];
|
|
}
|
|
|
|
/*
|
|
* We can represent the historical contribution to runnable average as the
|
|
* coefficients of a geometric series. To do this we sub-divide our runnable
|
|
* history into segments of approximately 1ms (1024us); label the segment that
|
|
* occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
|
|
*
|
|
* [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
|
|
* p0 p1 p2
|
|
* (now) (~1ms ago) (~2ms ago)
|
|
*
|
|
* Let u_i denote the fraction of p_i that the entity was runnable.
|
|
*
|
|
* We then designate the fractions u_i as our co-efficients, yielding the
|
|
* following representation of historical load:
|
|
* u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
|
|
*
|
|
* We choose y based on the with of a reasonably scheduling period, fixing:
|
|
* y^32 = 0.5
|
|
*
|
|
* This means that the contribution to load ~32ms ago (u_32) will be weighted
|
|
* approximately half as much as the contribution to load within the last ms
|
|
* (u_0).
|
|
*
|
|
* When a period "rolls over" and we have new u_0`, multiplying the previous
|
|
* sum again by y is sufficient to update:
|
|
* load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
|
|
* = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
|
|
*/
|
|
static __always_inline int __update_entity_runnable_avg(u64 now,
|
|
struct sched_avg *sa,
|
|
int runnable)
|
|
{
|
|
u64 delta, periods;
|
|
u32 runnable_contrib;
|
|
int delta_w, decayed = 0;
|
|
|
|
delta = now - sa->last_runnable_update;
|
|
/*
|
|
* This should only happen when time goes backwards, which it
|
|
* unfortunately does during sched clock init when we swap over to TSC.
|
|
*/
|
|
if ((s64)delta < 0) {
|
|
sa->last_runnable_update = now;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Use 1024ns as the unit of measurement since it's a reasonable
|
|
* approximation of 1us and fast to compute.
|
|
*/
|
|
delta >>= 10;
|
|
if (!delta)
|
|
return 0;
|
|
sa->last_runnable_update = now;
|
|
|
|
/* delta_w is the amount already accumulated against our next period */
|
|
delta_w = sa->runnable_avg_period % 1024;
|
|
if (delta + delta_w >= 1024) {
|
|
/* period roll-over */
|
|
decayed = 1;
|
|
|
|
/*
|
|
* Now that we know we're crossing a period boundary, figure
|
|
* out how much from delta we need to complete the current
|
|
* period and accrue it.
|
|
*/
|
|
delta_w = 1024 - delta_w;
|
|
if (runnable)
|
|
sa->runnable_avg_sum += delta_w;
|
|
sa->runnable_avg_period += delta_w;
|
|
|
|
delta -= delta_w;
|
|
|
|
/* Figure out how many additional periods this update spans */
|
|
periods = delta / 1024;
|
|
delta %= 1024;
|
|
|
|
sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
|
|
periods + 1);
|
|
sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
|
|
periods + 1);
|
|
|
|
/* Efficiently calculate \sum (1..n_period) 1024*y^i */
|
|
runnable_contrib = __compute_runnable_contrib(periods);
|
|
if (runnable)
|
|
sa->runnable_avg_sum += runnable_contrib;
|
|
sa->runnable_avg_period += runnable_contrib;
|
|
}
|
|
|
|
/* Remainder of delta accrued against u_0` */
|
|
if (runnable)
|
|
sa->runnable_avg_sum += delta;
|
|
sa->runnable_avg_period += delta;
|
|
|
|
return decayed;
|
|
}
|
|
|
|
/* Synchronize an entity's decay with its parenting cfs_rq.*/
|
|
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
u64 decays = atomic64_read(&cfs_rq->decay_counter);
|
|
|
|
decays -= se->avg.decay_count;
|
|
if (!decays)
|
|
return 0;
|
|
|
|
se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
|
|
se->avg.decay_count = 0;
|
|
|
|
return decays;
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
|
|
int force_update)
|
|
{
|
|
struct task_group *tg = cfs_rq->tg;
|
|
long tg_contrib;
|
|
|
|
tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
|
|
tg_contrib -= cfs_rq->tg_load_contrib;
|
|
|
|
if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
|
|
atomic_long_add(tg_contrib, &tg->load_avg);
|
|
cfs_rq->tg_load_contrib += tg_contrib;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Aggregate cfs_rq runnable averages into an equivalent task_group
|
|
* representation for computing load contributions.
|
|
*/
|
|
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
|
|
struct cfs_rq *cfs_rq)
|
|
{
|
|
struct task_group *tg = cfs_rq->tg;
|
|
long contrib;
|
|
|
|
/* The fraction of a cpu used by this cfs_rq */
|
|
contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
|
|
sa->runnable_avg_period + 1);
|
|
contrib -= cfs_rq->tg_runnable_contrib;
|
|
|
|
if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
|
|
atomic_add(contrib, &tg->runnable_avg);
|
|
cfs_rq->tg_runnable_contrib += contrib;
|
|
}
|
|
}
|
|
|
|
static inline void __update_group_entity_contrib(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *cfs_rq = group_cfs_rq(se);
|
|
struct task_group *tg = cfs_rq->tg;
|
|
int runnable_avg;
|
|
|
|
u64 contrib;
|
|
|
|
contrib = cfs_rq->tg_load_contrib * tg->shares;
|
|
se->avg.load_avg_contrib = div_u64(contrib,
|
|
atomic_long_read(&tg->load_avg) + 1);
|
|
|
|
/*
|
|
* For group entities we need to compute a correction term in the case
|
|
* that they are consuming <1 cpu so that we would contribute the same
|
|
* load as a task of equal weight.
|
|
*
|
|
* Explicitly co-ordinating this measurement would be expensive, but
|
|
* fortunately the sum of each cpus contribution forms a usable
|
|
* lower-bound on the true value.
|
|
*
|
|
* Consider the aggregate of 2 contributions. Either they are disjoint
|
|
* (and the sum represents true value) or they are disjoint and we are
|
|
* understating by the aggregate of their overlap.
|
|
*
|
|
* Extending this to N cpus, for a given overlap, the maximum amount we
|
|
* understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
|
|
* cpus that overlap for this interval and w_i is the interval width.
|
|
*
|
|
* On a small machine; the first term is well-bounded which bounds the
|
|
* total error since w_i is a subset of the period. Whereas on a
|
|
* larger machine, while this first term can be larger, if w_i is the
|
|
* of consequential size guaranteed to see n_i*w_i quickly converge to
|
|
* our upper bound of 1-cpu.
|
|
*/
|
|
runnable_avg = atomic_read(&tg->runnable_avg);
|
|
if (runnable_avg < NICE_0_LOAD) {
|
|
se->avg.load_avg_contrib *= runnable_avg;
|
|
se->avg.load_avg_contrib >>= NICE_0_SHIFT;
|
|
}
|
|
}
|
|
#else
|
|
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
|
|
int force_update) {}
|
|
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
|
|
struct cfs_rq *cfs_rq) {}
|
|
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
|
|
#endif
|
|
|
|
static inline void __update_task_entity_contrib(struct sched_entity *se)
|
|
{
|
|
u32 contrib;
|
|
|
|
/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
|
|
contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
|
|
contrib /= (se->avg.runnable_avg_period + 1);
|
|
se->avg.load_avg_contrib = scale_load(contrib);
|
|
}
|
|
|
|
/* Compute the current contribution to load_avg by se, return any delta */
|
|
static long __update_entity_load_avg_contrib(struct sched_entity *se)
|
|
{
|
|
long old_contrib = se->avg.load_avg_contrib;
|
|
|
|
if (entity_is_task(se)) {
|
|
__update_task_entity_contrib(se);
|
|
} else {
|
|
__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
|
|
__update_group_entity_contrib(se);
|
|
}
|
|
|
|
return se->avg.load_avg_contrib - old_contrib;
|
|
}
|
|
|
|
static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
|
|
long load_contrib)
|
|
{
|
|
if (likely(load_contrib < cfs_rq->blocked_load_avg))
|
|
cfs_rq->blocked_load_avg -= load_contrib;
|
|
else
|
|
cfs_rq->blocked_load_avg = 0;
|
|
}
|
|
|
|
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
|
|
|
|
/* Update a sched_entity's runnable average */
|
|
static inline void update_entity_load_avg(struct sched_entity *se,
|
|
int update_cfs_rq)
|
|
{
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
long contrib_delta;
|
|
u64 now;
|
|
|
|
/*
|
|
* For a group entity we need to use their owned cfs_rq_clock_task() in
|
|
* case they are the parent of a throttled hierarchy.
|
|
*/
|
|
if (entity_is_task(se))
|
|
now = cfs_rq_clock_task(cfs_rq);
|
|
else
|
|
now = cfs_rq_clock_task(group_cfs_rq(se));
|
|
|
|
if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
|
|
return;
|
|
|
|
contrib_delta = __update_entity_load_avg_contrib(se);
|
|
|
|
if (!update_cfs_rq)
|
|
return;
|
|
|
|
if (se->on_rq)
|
|
cfs_rq->runnable_load_avg += contrib_delta;
|
|
else
|
|
subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
|
|
}
|
|
|
|
/*
|
|
* Decay the load contributed by all blocked children and account this so that
|
|
* their contribution may appropriately discounted when they wake up.
|
|
*/
|
|
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
|
|
{
|
|
u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
|
|
u64 decays;
|
|
|
|
decays = now - cfs_rq->last_decay;
|
|
if (!decays && !force_update)
|
|
return;
|
|
|
|
if (atomic_long_read(&cfs_rq->removed_load)) {
|
|
unsigned long removed_load;
|
|
removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
|
|
subtract_blocked_load_contrib(cfs_rq, removed_load);
|
|
}
|
|
|
|
if (decays) {
|
|
cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
|
|
decays);
|
|
atomic64_add(decays, &cfs_rq->decay_counter);
|
|
cfs_rq->last_decay = now;
|
|
}
|
|
|
|
__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
|
|
}
|
|
|
|
static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
|
|
{
|
|
__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
|
|
__update_tg_runnable_avg(&rq->avg, &rq->cfs);
|
|
}
|
|
|
|
/* Add the load generated by se into cfs_rq's child load-average */
|
|
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
|
|
struct sched_entity *se,
|
|
int wakeup)
|
|
{
|
|
/*
|
|
* We track migrations using entity decay_count <= 0, on a wake-up
|
|
* migration we use a negative decay count to track the remote decays
|
|
* accumulated while sleeping.
|
|
*
|
|
* Newly forked tasks are enqueued with se->avg.decay_count == 0, they
|
|
* are seen by enqueue_entity_load_avg() as a migration with an already
|
|
* constructed load_avg_contrib.
|
|
*/
|
|
if (unlikely(se->avg.decay_count <= 0)) {
|
|
se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
|
|
if (se->avg.decay_count) {
|
|
/*
|
|
* In a wake-up migration we have to approximate the
|
|
* time sleeping. This is because we can't synchronize
|
|
* clock_task between the two cpus, and it is not
|
|
* guaranteed to be read-safe. Instead, we can
|
|
* approximate this using our carried decays, which are
|
|
* explicitly atomically readable.
|
|
*/
|
|
se->avg.last_runnable_update -= (-se->avg.decay_count)
|
|
<< 20;
|
|
update_entity_load_avg(se, 0);
|
|
/* Indicate that we're now synchronized and on-rq */
|
|
se->avg.decay_count = 0;
|
|
}
|
|
wakeup = 0;
|
|
} else {
|
|
/*
|
|
* Task re-woke on same cpu (or else migrate_task_rq_fair()
|
|
* would have made count negative); we must be careful to avoid
|
|
* double-accounting blocked time after synchronizing decays.
|
|
*/
|
|
se->avg.last_runnable_update += __synchronize_entity_decay(se)
|
|
<< 20;
|
|
}
|
|
|
|
/* migrated tasks did not contribute to our blocked load */
|
|
if (wakeup) {
|
|
subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
|
|
update_entity_load_avg(se, 0);
|
|
}
|
|
|
|
cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
|
|
/* we force update consideration on load-balancer moves */
|
|
update_cfs_rq_blocked_load(cfs_rq, !wakeup);
|
|
}
|
|
|
|
/*
|
|
* Remove se's load from this cfs_rq child load-average, if the entity is
|
|
* transitioning to a blocked state we track its projected decay using
|
|
* blocked_load_avg.
|
|
*/
|
|
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
|
|
struct sched_entity *se,
|
|
int sleep)
|
|
{
|
|
update_entity_load_avg(se, 1);
|
|
/* we force update consideration on load-balancer moves */
|
|
update_cfs_rq_blocked_load(cfs_rq, !sleep);
|
|
|
|
cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
|
|
if (sleep) {
|
|
cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
|
|
se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
|
|
} /* migrations, e.g. sleep=0 leave decay_count == 0 */
|
|
}
|
|
|
|
/*
|
|
* Update the rq's load with the elapsed running time before entering
|
|
* idle. if the last scheduled task is not a CFS task, idle_enter will
|
|
* be the only way to update the runnable statistic.
|
|
*/
|
|
void idle_enter_fair(struct rq *this_rq)
|
|
{
|
|
update_rq_runnable_avg(this_rq, 1);
|
|
}
|
|
|
|
/*
|
|
* Update the rq's load with the elapsed idle time before a task is
|
|
* scheduled. if the newly scheduled task is not a CFS task, idle_exit will
|
|
* be the only way to update the runnable statistic.
|
|
*/
|
|
void idle_exit_fair(struct rq *this_rq)
|
|
{
|
|
update_rq_runnable_avg(this_rq, 0);
|
|
}
|
|
|
|
#else
|
|
static inline void update_entity_load_avg(struct sched_entity *se,
|
|
int update_cfs_rq) {}
|
|
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
|
|
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
|
|
struct sched_entity *se,
|
|
int wakeup) {}
|
|
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
|
|
struct sched_entity *se,
|
|
int sleep) {}
|
|
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
|
|
int force_update) {}
|
|
#endif
|
|
|
|
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
struct task_struct *tsk = NULL;
|
|
|
|
if (entity_is_task(se))
|
|
tsk = task_of(se);
|
|
|
|
if (se->statistics.sleep_start) {
|
|
u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
|
|
|
|
if ((s64)delta < 0)
|
|
delta = 0;
|
|
|
|
if (unlikely(delta > se->statistics.sleep_max))
|
|
se->statistics.sleep_max = delta;
|
|
|
|
se->statistics.sleep_start = 0;
|
|
se->statistics.sum_sleep_runtime += delta;
|
|
|
|
if (tsk) {
|
|
account_scheduler_latency(tsk, delta >> 10, 1);
|
|
trace_sched_stat_sleep(tsk, delta);
|
|
}
|
|
}
|
|
if (se->statistics.block_start) {
|
|
u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
|
|
|
|
if ((s64)delta < 0)
|
|
delta = 0;
|
|
|
|
if (unlikely(delta > se->statistics.block_max))
|
|
se->statistics.block_max = delta;
|
|
|
|
se->statistics.block_start = 0;
|
|
se->statistics.sum_sleep_runtime += delta;
|
|
|
|
if (tsk) {
|
|
if (tsk->in_iowait) {
|
|
se->statistics.iowait_sum += delta;
|
|
se->statistics.iowait_count++;
|
|
trace_sched_stat_iowait(tsk, delta);
|
|
}
|
|
|
|
trace_sched_stat_blocked(tsk, delta);
|
|
|
|
/*
|
|
* Blocking time is in units of nanosecs, so shift by
|
|
* 20 to get a milliseconds-range estimation of the
|
|
* amount of time that the task spent sleeping:
|
|
*/
|
|
if (unlikely(prof_on == SLEEP_PROFILING)) {
|
|
profile_hits(SLEEP_PROFILING,
|
|
(void *)get_wchan(tsk),
|
|
delta >> 20);
|
|
}
|
|
account_scheduler_latency(tsk, delta >> 10, 0);
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
|
|
static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
s64 d = se->vruntime - cfs_rq->min_vruntime;
|
|
|
|
if (d < 0)
|
|
d = -d;
|
|
|
|
if (d > 3*sysctl_sched_latency)
|
|
schedstat_inc(cfs_rq, nr_spread_over);
|
|
#endif
|
|
}
|
|
|
|
static void
|
|
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
|
|
{
|
|
u64 vruntime = cfs_rq->min_vruntime;
|
|
|
|
/*
|
|
* The 'current' period is already promised to the current tasks,
|
|
* however the extra weight of the new task will slow them down a
|
|
* little, place the new task so that it fits in the slot that
|
|
* stays open at the end.
|
|
*/
|
|
if (initial && sched_feat(START_DEBIT))
|
|
vruntime += sched_vslice(cfs_rq, se);
|
|
|
|
/* sleeps up to a single latency don't count. */
|
|
if (!initial) {
|
|
unsigned long thresh = sysctl_sched_latency;
|
|
|
|
/*
|
|
* Halve their sleep time's effect, to allow
|
|
* for a gentler effect of sleepers:
|
|
*/
|
|
if (sched_feat(GENTLE_FAIR_SLEEPERS))
|
|
thresh >>= 1;
|
|
|
|
vruntime -= thresh;
|
|
}
|
|
|
|
/* ensure we never gain time by being placed backwards. */
|
|
se->vruntime = max_vruntime(se->vruntime, vruntime);
|
|
}
|
|
|
|
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
|
|
|
|
static void
|
|
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
/*
|
|
* Update the normalized vruntime before updating min_vruntime
|
|
* through calling update_curr().
|
|
*/
|
|
if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
|
|
se->vruntime += cfs_rq->min_vruntime;
|
|
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
|
|
account_entity_enqueue(cfs_rq, se);
|
|
update_cfs_shares(cfs_rq);
|
|
|
|
if (flags & ENQUEUE_WAKEUP) {
|
|
place_entity(cfs_rq, se, 0);
|
|
enqueue_sleeper(cfs_rq, se);
|
|
}
|
|
|
|
update_stats_enqueue(cfs_rq, se);
|
|
check_spread(cfs_rq, se);
|
|
if (se != cfs_rq->curr)
|
|
__enqueue_entity(cfs_rq, se);
|
|
se->on_rq = 1;
|
|
|
|
if (cfs_rq->nr_running == 1) {
|
|
list_add_leaf_cfs_rq(cfs_rq);
|
|
check_enqueue_throttle(cfs_rq);
|
|
}
|
|
}
|
|
|
|
static void __clear_buddies_last(struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
if (cfs_rq->last == se)
|
|
cfs_rq->last = NULL;
|
|
else
|
|
break;
|
|
}
|
|
}
|
|
|
|
static void __clear_buddies_next(struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
if (cfs_rq->next == se)
|
|
cfs_rq->next = NULL;
|
|
else
|
|
break;
|
|
}
|
|
}
|
|
|
|
static void __clear_buddies_skip(struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
if (cfs_rq->skip == se)
|
|
cfs_rq->skip = NULL;
|
|
else
|
|
break;
|
|
}
|
|
}
|
|
|
|
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
if (cfs_rq->last == se)
|
|
__clear_buddies_last(se);
|
|
|
|
if (cfs_rq->next == se)
|
|
__clear_buddies_next(se);
|
|
|
|
if (cfs_rq->skip == se)
|
|
__clear_buddies_skip(se);
|
|
}
|
|
|
|
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
|
|
|
|
static void
|
|
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
|
|
|
|
update_stats_dequeue(cfs_rq, se);
|
|
if (flags & DEQUEUE_SLEEP) {
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
if (entity_is_task(se)) {
|
|
struct task_struct *tsk = task_of(se);
|
|
|
|
if (tsk->state & TASK_INTERRUPTIBLE)
|
|
se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
|
|
if (tsk->state & TASK_UNINTERRUPTIBLE)
|
|
se->statistics.block_start = rq_clock(rq_of(cfs_rq));
|
|
}
|
|
#endif
|
|
}
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
if (se != cfs_rq->curr)
|
|
__dequeue_entity(cfs_rq, se);
|
|
se->on_rq = 0;
|
|
account_entity_dequeue(cfs_rq, se);
|
|
|
|
/*
|
|
* Normalize the entity after updating the min_vruntime because the
|
|
* update can refer to the ->curr item and we need to reflect this
|
|
* movement in our normalized position.
|
|
*/
|
|
if (!(flags & DEQUEUE_SLEEP))
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
|
|
/* return excess runtime on last dequeue */
|
|
return_cfs_rq_runtime(cfs_rq);
|
|
|
|
update_min_vruntime(cfs_rq);
|
|
update_cfs_shares(cfs_rq);
|
|
}
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void
|
|
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
|
|
{
|
|
unsigned long ideal_runtime, delta_exec;
|
|
struct sched_entity *se;
|
|
s64 delta;
|
|
|
|
ideal_runtime = sched_slice(cfs_rq, curr);
|
|
delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
|
|
if (delta_exec > ideal_runtime) {
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
/*
|
|
* The current task ran long enough, ensure it doesn't get
|
|
* re-elected due to buddy favours.
|
|
*/
|
|
clear_buddies(cfs_rq, curr);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Ensure that a task that missed wakeup preemption by a
|
|
* narrow margin doesn't have to wait for a full slice.
|
|
* This also mitigates buddy induced latencies under load.
|
|
*/
|
|
if (delta_exec < sysctl_sched_min_granularity)
|
|
return;
|
|
|
|
se = __pick_first_entity(cfs_rq);
|
|
delta = curr->vruntime - se->vruntime;
|
|
|
|
if (delta < 0)
|
|
return;
|
|
|
|
if (delta > ideal_runtime)
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
}
|
|
|
|
static void
|
|
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/* 'current' is not kept within the tree. */
|
|
if (se->on_rq) {
|
|
/*
|
|
* Any task has to be enqueued before it get to execute on
|
|
* a CPU. So account for the time it spent waiting on the
|
|
* runqueue.
|
|
*/
|
|
update_stats_wait_end(cfs_rq, se);
|
|
__dequeue_entity(cfs_rq, se);
|
|
}
|
|
|
|
update_stats_curr_start(cfs_rq, se);
|
|
cfs_rq->curr = se;
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
/*
|
|
* Track our maximum slice length, if the CPU's load is at
|
|
* least twice that of our own weight (i.e. dont track it
|
|
* when there are only lesser-weight tasks around):
|
|
*/
|
|
if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
|
|
se->statistics.slice_max = max(se->statistics.slice_max,
|
|
se->sum_exec_runtime - se->prev_sum_exec_runtime);
|
|
}
|
|
#endif
|
|
se->prev_sum_exec_runtime = se->sum_exec_runtime;
|
|
}
|
|
|
|
static int
|
|
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
|
|
|
|
/*
|
|
* Pick the next process, keeping these things in mind, in this order:
|
|
* 1) keep things fair between processes/task groups
|
|
* 2) pick the "next" process, since someone really wants that to run
|
|
* 3) pick the "last" process, for cache locality
|
|
* 4) do not run the "skip" process, if something else is available
|
|
*/
|
|
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct sched_entity *se = __pick_first_entity(cfs_rq);
|
|
struct sched_entity *left = se;
|
|
|
|
/*
|
|
* Avoid running the skip buddy, if running something else can
|
|
* be done without getting too unfair.
|
|
*/
|
|
if (cfs_rq->skip == se) {
|
|
struct sched_entity *second = __pick_next_entity(se);
|
|
if (second && wakeup_preempt_entity(second, left) < 1)
|
|
se = second;
|
|
}
|
|
|
|
/*
|
|
* Prefer last buddy, try to return the CPU to a preempted task.
|
|
*/
|
|
if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
|
|
se = cfs_rq->last;
|
|
|
|
/*
|
|
* Someone really wants this to run. If it's not unfair, run it.
|
|
*/
|
|
if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
|
|
se = cfs_rq->next;
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
return se;
|
|
}
|
|
|
|
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
|
|
|
|
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
|
|
{
|
|
/*
|
|
* If still on the runqueue then deactivate_task()
|
|
* was not called and update_curr() has to be done:
|
|
*/
|
|
if (prev->on_rq)
|
|
update_curr(cfs_rq);
|
|
|
|
/* throttle cfs_rqs exceeding runtime */
|
|
check_cfs_rq_runtime(cfs_rq);
|
|
|
|
check_spread(cfs_rq, prev);
|
|
if (prev->on_rq) {
|
|
update_stats_wait_start(cfs_rq, prev);
|
|
/* Put 'current' back into the tree. */
|
|
__enqueue_entity(cfs_rq, prev);
|
|
/* in !on_rq case, update occurred at dequeue */
|
|
update_entity_load_avg(prev, 1);
|
|
}
|
|
cfs_rq->curr = NULL;
|
|
}
|
|
|
|
static void
|
|
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
/*
|
|
* Ensure that runnable average is periodically updated.
|
|
*/
|
|
update_entity_load_avg(curr, 1);
|
|
update_cfs_rq_blocked_load(cfs_rq, 1);
|
|
update_cfs_shares(cfs_rq);
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
/*
|
|
* queued ticks are scheduled to match the slice, so don't bother
|
|
* validating it and just reschedule.
|
|
*/
|
|
if (queued) {
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
return;
|
|
}
|
|
/*
|
|
* don't let the period tick interfere with the hrtick preemption
|
|
*/
|
|
if (!sched_feat(DOUBLE_TICK) &&
|
|
hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
|
|
return;
|
|
#endif
|
|
|
|
if (cfs_rq->nr_running > 1)
|
|
check_preempt_tick(cfs_rq, curr);
|
|
}
|
|
|
|
|
|
/**************************************************
|
|
* CFS bandwidth control machinery
|
|
*/
|
|
|
|
#ifdef CONFIG_CFS_BANDWIDTH
|
|
|
|
#ifdef HAVE_JUMP_LABEL
|
|
static struct static_key __cfs_bandwidth_used;
|
|
|
|
static inline bool cfs_bandwidth_used(void)
|
|
{
|
|
return static_key_false(&__cfs_bandwidth_used);
|
|
}
|
|
|
|
void cfs_bandwidth_usage_inc(void)
|
|
{
|
|
static_key_slow_inc(&__cfs_bandwidth_used);
|
|
}
|
|
|
|
void cfs_bandwidth_usage_dec(void)
|
|
{
|
|
static_key_slow_dec(&__cfs_bandwidth_used);
|
|
}
|
|
#else /* HAVE_JUMP_LABEL */
|
|
static bool cfs_bandwidth_used(void)
|
|
{
|
|
return true;
|
|
}
|
|
|
|
void cfs_bandwidth_usage_inc(void) {}
|
|
void cfs_bandwidth_usage_dec(void) {}
|
|
#endif /* HAVE_JUMP_LABEL */
|
|
|
|
/*
|
|
* default period for cfs group bandwidth.
|
|
* default: 0.1s, units: nanoseconds
|
|
*/
|
|
static inline u64 default_cfs_period(void)
|
|
{
|
|
return 100000000ULL;
|
|
}
|
|
|
|
static inline u64 sched_cfs_bandwidth_slice(void)
|
|
{
|
|
return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
|
|
}
|
|
|
|
/*
|
|
* Replenish runtime according to assigned quota and update expiration time.
|
|
* We use sched_clock_cpu directly instead of rq->clock to avoid adding
|
|
* additional synchronization around rq->lock.
|
|
*
|
|
* requires cfs_b->lock
|
|
*/
|
|
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
u64 now;
|
|
|
|
if (cfs_b->quota == RUNTIME_INF)
|
|
return;
|
|
|
|
now = sched_clock_cpu(smp_processor_id());
|
|
cfs_b->runtime = cfs_b->quota;
|
|
cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
|
|
}
|
|
|
|
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
|
|
{
|
|
return &tg->cfs_bandwidth;
|
|
}
|
|
|
|
/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
|
|
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (unlikely(cfs_rq->throttle_count))
|
|
return cfs_rq->throttled_clock_task;
|
|
|
|
return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
|
|
}
|
|
|
|
/* returns 0 on failure to allocate runtime */
|
|
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct task_group *tg = cfs_rq->tg;
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
|
|
u64 amount = 0, min_amount, expires;
|
|
|
|
/* note: this is a positive sum as runtime_remaining <= 0 */
|
|
min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
if (cfs_b->quota == RUNTIME_INF)
|
|
amount = min_amount;
|
|
else {
|
|
/*
|
|
* If the bandwidth pool has become inactive, then at least one
|
|
* period must have elapsed since the last consumption.
|
|
* Refresh the global state and ensure bandwidth timer becomes
|
|
* active.
|
|
*/
|
|
if (!cfs_b->timer_active) {
|
|
__refill_cfs_bandwidth_runtime(cfs_b);
|
|
__start_cfs_bandwidth(cfs_b);
|
|
}
|
|
|
|
if (cfs_b->runtime > 0) {
|
|
amount = min(cfs_b->runtime, min_amount);
|
|
cfs_b->runtime -= amount;
|
|
cfs_b->idle = 0;
|
|
}
|
|
}
|
|
expires = cfs_b->runtime_expires;
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
|
|
cfs_rq->runtime_remaining += amount;
|
|
/*
|
|
* we may have advanced our local expiration to account for allowed
|
|
* spread between our sched_clock and the one on which runtime was
|
|
* issued.
|
|
*/
|
|
if ((s64)(expires - cfs_rq->runtime_expires) > 0)
|
|
cfs_rq->runtime_expires = expires;
|
|
|
|
return cfs_rq->runtime_remaining > 0;
|
|
}
|
|
|
|
/*
|
|
* Note: This depends on the synchronization provided by sched_clock and the
|
|
* fact that rq->clock snapshots this value.
|
|
*/
|
|
static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
|
|
/* if the deadline is ahead of our clock, nothing to do */
|
|
if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
|
|
return;
|
|
|
|
if (cfs_rq->runtime_remaining < 0)
|
|
return;
|
|
|
|
/*
|
|
* If the local deadline has passed we have to consider the
|
|
* possibility that our sched_clock is 'fast' and the global deadline
|
|
* has not truly expired.
|
|
*
|
|
* Fortunately we can check determine whether this the case by checking
|
|
* whether the global deadline has advanced.
|
|
*/
|
|
|
|
if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
|
|
/* extend local deadline, drift is bounded above by 2 ticks */
|
|
cfs_rq->runtime_expires += TICK_NSEC;
|
|
} else {
|
|
/* global deadline is ahead, expiration has passed */
|
|
cfs_rq->runtime_remaining = 0;
|
|
}
|
|
}
|
|
|
|
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
|
|
{
|
|
/* dock delta_exec before expiring quota (as it could span periods) */
|
|
cfs_rq->runtime_remaining -= delta_exec;
|
|
expire_cfs_rq_runtime(cfs_rq);
|
|
|
|
if (likely(cfs_rq->runtime_remaining > 0))
|
|
return;
|
|
|
|
/*
|
|
* if we're unable to extend our runtime we resched so that the active
|
|
* hierarchy can be throttled
|
|
*/
|
|
if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
}
|
|
|
|
static __always_inline
|
|
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
|
|
{
|
|
if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
|
|
return;
|
|
|
|
__account_cfs_rq_runtime(cfs_rq, delta_exec);
|
|
}
|
|
|
|
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
|
|
{
|
|
return cfs_bandwidth_used() && cfs_rq->throttled;
|
|
}
|
|
|
|
/* check whether cfs_rq, or any parent, is throttled */
|
|
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
|
|
{
|
|
return cfs_bandwidth_used() && cfs_rq->throttle_count;
|
|
}
|
|
|
|
/*
|
|
* Ensure that neither of the group entities corresponding to src_cpu or
|
|
* dest_cpu are members of a throttled hierarchy when performing group
|
|
* load-balance operations.
|
|
*/
|
|
static inline int throttled_lb_pair(struct task_group *tg,
|
|
int src_cpu, int dest_cpu)
|
|
{
|
|
struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
|
|
|
|
src_cfs_rq = tg->cfs_rq[src_cpu];
|
|
dest_cfs_rq = tg->cfs_rq[dest_cpu];
|
|
|
|
return throttled_hierarchy(src_cfs_rq) ||
|
|
throttled_hierarchy(dest_cfs_rq);
|
|
}
|
|
|
|
/* updated child weight may affect parent so we have to do this bottom up */
|
|
static int tg_unthrottle_up(struct task_group *tg, void *data)
|
|
{
|
|
struct rq *rq = data;
|
|
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
|
|
|
|
cfs_rq->throttle_count--;
|
|
#ifdef CONFIG_SMP
|
|
if (!cfs_rq->throttle_count) {
|
|
/* adjust cfs_rq_clock_task() */
|
|
cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
|
|
cfs_rq->throttled_clock_task;
|
|
}
|
|
#endif
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int tg_throttle_down(struct task_group *tg, void *data)
|
|
{
|
|
struct rq *rq = data;
|
|
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
|
|
|
|
/* group is entering throttled state, stop time */
|
|
if (!cfs_rq->throttle_count)
|
|
cfs_rq->throttled_clock_task = rq_clock_task(rq);
|
|
cfs_rq->throttle_count++;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
struct sched_entity *se;
|
|
long task_delta, dequeue = 1;
|
|
|
|
se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
|
|
|
|
/* freeze hierarchy runnable averages while throttled */
|
|
rcu_read_lock();
|
|
walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
|
|
rcu_read_unlock();
|
|
|
|
task_delta = cfs_rq->h_nr_running;
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
|
|
/* throttled entity or throttle-on-deactivate */
|
|
if (!se->on_rq)
|
|
break;
|
|
|
|
if (dequeue)
|
|
dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
|
|
qcfs_rq->h_nr_running -= task_delta;
|
|
|
|
if (qcfs_rq->load.weight)
|
|
dequeue = 0;
|
|
}
|
|
|
|
if (!se)
|
|
rq->nr_running -= task_delta;
|
|
|
|
cfs_rq->throttled = 1;
|
|
cfs_rq->throttled_clock = rq_clock(rq);
|
|
raw_spin_lock(&cfs_b->lock);
|
|
list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
|
|
if (!cfs_b->timer_active)
|
|
__start_cfs_bandwidth(cfs_b);
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
}
|
|
|
|
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
struct sched_entity *se;
|
|
int enqueue = 1;
|
|
long task_delta;
|
|
|
|
se = cfs_rq->tg->se[cpu_of(rq)];
|
|
|
|
cfs_rq->throttled = 0;
|
|
|
|
update_rq_clock(rq);
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
|
|
list_del_rcu(&cfs_rq->throttled_list);
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
|
|
/* update hierarchical throttle state */
|
|
walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
|
|
|
|
if (!cfs_rq->load.weight)
|
|
return;
|
|
|
|
task_delta = cfs_rq->h_nr_running;
|
|
for_each_sched_entity(se) {
|
|
if (se->on_rq)
|
|
enqueue = 0;
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
|
if (enqueue)
|
|
enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
|
|
cfs_rq->h_nr_running += task_delta;
|
|
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
}
|
|
|
|
if (!se)
|
|
rq->nr_running += task_delta;
|
|
|
|
/* determine whether we need to wake up potentially idle cpu */
|
|
if (rq->curr == rq->idle && rq->cfs.nr_running)
|
|
resched_task(rq->curr);
|
|
}
|
|
|
|
static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
|
|
u64 remaining, u64 expires)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
u64 runtime = remaining;
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
|
|
throttled_list) {
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
|
|
raw_spin_lock(&rq->lock);
|
|
if (!cfs_rq_throttled(cfs_rq))
|
|
goto next;
|
|
|
|
runtime = -cfs_rq->runtime_remaining + 1;
|
|
if (runtime > remaining)
|
|
runtime = remaining;
|
|
remaining -= runtime;
|
|
|
|
cfs_rq->runtime_remaining += runtime;
|
|
cfs_rq->runtime_expires = expires;
|
|
|
|
/* we check whether we're throttled above */
|
|
if (cfs_rq->runtime_remaining > 0)
|
|
unthrottle_cfs_rq(cfs_rq);
|
|
|
|
next:
|
|
raw_spin_unlock(&rq->lock);
|
|
|
|
if (!remaining)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return remaining;
|
|
}
|
|
|
|
/*
|
|
* Responsible for refilling a task_group's bandwidth and unthrottling its
|
|
* cfs_rqs as appropriate. If there has been no activity within the last
|
|
* period the timer is deactivated until scheduling resumes; cfs_b->idle is
|
|
* used to track this state.
|
|
*/
|
|
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
|
|
{
|
|
u64 runtime, runtime_expires;
|
|
int idle = 1, throttled;
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
/* no need to continue the timer with no bandwidth constraint */
|
|
if (cfs_b->quota == RUNTIME_INF)
|
|
goto out_unlock;
|
|
|
|
throttled = !list_empty(&cfs_b->throttled_cfs_rq);
|
|
/* idle depends on !throttled (for the case of a large deficit) */
|
|
idle = cfs_b->idle && !throttled;
|
|
cfs_b->nr_periods += overrun;
|
|
|
|
/* if we're going inactive then everything else can be deferred */
|
|
if (idle)
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* if we have relooped after returning idle once, we need to update our
|
|
* status as actually running, so that other cpus doing
|
|
* __start_cfs_bandwidth will stop trying to cancel us.
|
|
*/
|
|
cfs_b->timer_active = 1;
|
|
|
|
__refill_cfs_bandwidth_runtime(cfs_b);
|
|
|
|
if (!throttled) {
|
|
/* mark as potentially idle for the upcoming period */
|
|
cfs_b->idle = 1;
|
|
goto out_unlock;
|
|
}
|
|
|
|
/* account preceding periods in which throttling occurred */
|
|
cfs_b->nr_throttled += overrun;
|
|
|
|
/*
|
|
* There are throttled entities so we must first use the new bandwidth
|
|
* to unthrottle them before making it generally available. This
|
|
* ensures that all existing debts will be paid before a new cfs_rq is
|
|
* allowed to run.
|
|
*/
|
|
runtime = cfs_b->runtime;
|
|
runtime_expires = cfs_b->runtime_expires;
|
|
cfs_b->runtime = 0;
|
|
|
|
/*
|
|
* This check is repeated as we are holding onto the new bandwidth
|
|
* while we unthrottle. This can potentially race with an unthrottled
|
|
* group trying to acquire new bandwidth from the global pool.
|
|
*/
|
|
while (throttled && runtime > 0) {
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
/* we can't nest cfs_b->lock while distributing bandwidth */
|
|
runtime = distribute_cfs_runtime(cfs_b, runtime,
|
|
runtime_expires);
|
|
raw_spin_lock(&cfs_b->lock);
|
|
|
|
throttled = !list_empty(&cfs_b->throttled_cfs_rq);
|
|
}
|
|
|
|
/* return (any) remaining runtime */
|
|
cfs_b->runtime = runtime;
|
|
/*
|
|
* While we are ensured activity in the period following an
|
|
* unthrottle, this also covers the case in which the new bandwidth is
|
|
* insufficient to cover the existing bandwidth deficit. (Forcing the
|
|
* timer to remain active while there are any throttled entities.)
|
|
*/
|
|
cfs_b->idle = 0;
|
|
out_unlock:
|
|
if (idle)
|
|
cfs_b->timer_active = 0;
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
|
|
return idle;
|
|
}
|
|
|
|
/* a cfs_rq won't donate quota below this amount */
|
|
static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
|
|
/* minimum remaining period time to redistribute slack quota */
|
|
static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
|
|
/* how long we wait to gather additional slack before distributing */
|
|
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
|
|
|
|
/*
|
|
* Are we near the end of the current quota period?
|
|
*
|
|
* Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
|
|
* hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
|
|
* migrate_hrtimers, base is never cleared, so we are fine.
|
|
*/
|
|
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
|
|
{
|
|
struct hrtimer *refresh_timer = &cfs_b->period_timer;
|
|
u64 remaining;
|
|
|
|
/* if the call-back is running a quota refresh is already occurring */
|
|
if (hrtimer_callback_running(refresh_timer))
|
|
return 1;
|
|
|
|
/* is a quota refresh about to occur? */
|
|
remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
|
|
if (remaining < min_expire)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
|
|
|
|
/* if there's a quota refresh soon don't bother with slack */
|
|
if (runtime_refresh_within(cfs_b, min_left))
|
|
return;
|
|
|
|
start_bandwidth_timer(&cfs_b->slack_timer,
|
|
ns_to_ktime(cfs_bandwidth_slack_period));
|
|
}
|
|
|
|
/* we know any runtime found here is valid as update_curr() precedes return */
|
|
static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
|
|
|
|
if (slack_runtime <= 0)
|
|
return;
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
if (cfs_b->quota != RUNTIME_INF &&
|
|
cfs_rq->runtime_expires == cfs_b->runtime_expires) {
|
|
cfs_b->runtime += slack_runtime;
|
|
|
|
/* we are under rq->lock, defer unthrottling using a timer */
|
|
if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
|
|
!list_empty(&cfs_b->throttled_cfs_rq))
|
|
start_cfs_slack_bandwidth(cfs_b);
|
|
}
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
|
|
/* even if it's not valid for return we don't want to try again */
|
|
cfs_rq->runtime_remaining -= slack_runtime;
|
|
}
|
|
|
|
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (!cfs_bandwidth_used())
|
|
return;
|
|
|
|
if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
|
|
return;
|
|
|
|
__return_cfs_rq_runtime(cfs_rq);
|
|
}
|
|
|
|
/*
|
|
* This is done with a timer (instead of inline with bandwidth return) since
|
|
* it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
|
|
*/
|
|
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
|
|
u64 expires;
|
|
|
|
/* confirm we're still not at a refresh boundary */
|
|
raw_spin_lock(&cfs_b->lock);
|
|
if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
return;
|
|
}
|
|
|
|
if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
|
|
runtime = cfs_b->runtime;
|
|
cfs_b->runtime = 0;
|
|
}
|
|
expires = cfs_b->runtime_expires;
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
|
|
if (!runtime)
|
|
return;
|
|
|
|
runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
if (expires == cfs_b->runtime_expires)
|
|
cfs_b->runtime = runtime;
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
}
|
|
|
|
/*
|
|
* When a group wakes up we want to make sure that its quota is not already
|
|
* expired/exceeded, otherwise it may be allowed to steal additional ticks of
|
|
* runtime as update_curr() throttling can not not trigger until it's on-rq.
|
|
*/
|
|
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (!cfs_bandwidth_used())
|
|
return;
|
|
|
|
/* an active group must be handled by the update_curr()->put() path */
|
|
if (!cfs_rq->runtime_enabled || cfs_rq->curr)
|
|
return;
|
|
|
|
/* ensure the group is not already throttled */
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
return;
|
|
|
|
/* update runtime allocation */
|
|
account_cfs_rq_runtime(cfs_rq, 0);
|
|
if (cfs_rq->runtime_remaining <= 0)
|
|
throttle_cfs_rq(cfs_rq);
|
|
}
|
|
|
|
/* conditionally throttle active cfs_rq's from put_prev_entity() */
|
|
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (!cfs_bandwidth_used())
|
|
return;
|
|
|
|
if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
|
|
return;
|
|
|
|
/*
|
|
* it's possible for a throttled entity to be forced into a running
|
|
* state (e.g. set_curr_task), in this case we're finished.
|
|
*/
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
return;
|
|
|
|
throttle_cfs_rq(cfs_rq);
|
|
}
|
|
|
|
static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
|
|
{
|
|
struct cfs_bandwidth *cfs_b =
|
|
container_of(timer, struct cfs_bandwidth, slack_timer);
|
|
do_sched_cfs_slack_timer(cfs_b);
|
|
|
|
return HRTIMER_NORESTART;
|
|
}
|
|
|
|
static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
|
|
{
|
|
struct cfs_bandwidth *cfs_b =
|
|
container_of(timer, struct cfs_bandwidth, period_timer);
|
|
ktime_t now;
|
|
int overrun;
|
|
int idle = 0;
|
|
|
|
for (;;) {
|
|
now = hrtimer_cb_get_time(timer);
|
|
overrun = hrtimer_forward(timer, now, cfs_b->period);
|
|
|
|
if (!overrun)
|
|
break;
|
|
|
|
idle = do_sched_cfs_period_timer(cfs_b, overrun);
|
|
}
|
|
|
|
return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
|
|
}
|
|
|
|
void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
raw_spin_lock_init(&cfs_b->lock);
|
|
cfs_b->runtime = 0;
|
|
cfs_b->quota = RUNTIME_INF;
|
|
cfs_b->period = ns_to_ktime(default_cfs_period());
|
|
|
|
INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
|
|
hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
|
|
cfs_b->period_timer.function = sched_cfs_period_timer;
|
|
hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
|
|
cfs_b->slack_timer.function = sched_cfs_slack_timer;
|
|
}
|
|
|
|
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
cfs_rq->runtime_enabled = 0;
|
|
INIT_LIST_HEAD(&cfs_rq->throttled_list);
|
|
}
|
|
|
|
/* requires cfs_b->lock, may release to reprogram timer */
|
|
void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
/*
|
|
* The timer may be active because we're trying to set a new bandwidth
|
|
* period or because we're racing with the tear-down path
|
|
* (timer_active==0 becomes visible before the hrtimer call-back
|
|
* terminates). In either case we ensure that it's re-programmed
|
|
*/
|
|
while (unlikely(hrtimer_active(&cfs_b->period_timer)) &&
|
|
hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) {
|
|
/* bounce the lock to allow do_sched_cfs_period_timer to run */
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
cpu_relax();
|
|
raw_spin_lock(&cfs_b->lock);
|
|
/* if someone else restarted the timer then we're done */
|
|
if (cfs_b->timer_active)
|
|
return;
|
|
}
|
|
|
|
cfs_b->timer_active = 1;
|
|
start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
|
|
}
|
|
|
|
static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
hrtimer_cancel(&cfs_b->period_timer);
|
|
hrtimer_cancel(&cfs_b->slack_timer);
|
|
}
|
|
|
|
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
for_each_leaf_cfs_rq(rq, cfs_rq) {
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
|
|
if (!cfs_rq->runtime_enabled)
|
|
continue;
|
|
|
|
/*
|
|
* clock_task is not advancing so we just need to make sure
|
|
* there's some valid quota amount
|
|
*/
|
|
cfs_rq->runtime_remaining = cfs_b->quota;
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
unthrottle_cfs_rq(cfs_rq);
|
|
}
|
|
}
|
|
|
|
#else /* CONFIG_CFS_BANDWIDTH */
|
|
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
|
|
{
|
|
return rq_clock_task(rq_of(cfs_rq));
|
|
}
|
|
|
|
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
|
|
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
|
|
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
|
|
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
|
|
|
|
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline int throttled_lb_pair(struct task_group *tg,
|
|
int src_cpu, int dest_cpu)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
|
|
#endif
|
|
|
|
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
|
|
{
|
|
return NULL;
|
|
}
|
|
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
|
|
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
|
|
|
|
#endif /* CONFIG_CFS_BANDWIDTH */
|
|
|
|
/**************************************************
|
|
* CFS operations on tasks:
|
|
*/
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
WARN_ON(task_rq(p) != rq);
|
|
|
|
if (cfs_rq->nr_running > 1) {
|
|
u64 slice = sched_slice(cfs_rq, se);
|
|
u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
|
|
s64 delta = slice - ran;
|
|
|
|
if (delta < 0) {
|
|
if (rq->curr == p)
|
|
resched_task(p);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Don't schedule slices shorter than 10000ns, that just
|
|
* doesn't make sense. Rely on vruntime for fairness.
|
|
*/
|
|
if (rq->curr != p)
|
|
delta = max_t(s64, 10000LL, delta);
|
|
|
|
hrtick_start(rq, delta);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* called from enqueue/dequeue and updates the hrtick when the
|
|
* current task is from our class and nr_running is low enough
|
|
* to matter.
|
|
*/
|
|
static void hrtick_update(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
|
|
if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
|
|
return;
|
|
|
|
if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
|
|
hrtick_start_fair(rq, curr);
|
|
}
|
|
#else /* !CONFIG_SCHED_HRTICK */
|
|
static inline void
|
|
hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
|
|
static inline void hrtick_update(struct rq *rq)
|
|
{
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* The enqueue_task method is called before nr_running is
|
|
* increased. Here we update the fair scheduling stats and
|
|
* then put the task into the rbtree:
|
|
*/
|
|
static void
|
|
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
if (se->on_rq)
|
|
break;
|
|
cfs_rq = cfs_rq_of(se);
|
|
enqueue_entity(cfs_rq, se, flags);
|
|
|
|
/*
|
|
* end evaluation on encountering a throttled cfs_rq
|
|
*
|
|
* note: in the case of encountering a throttled cfs_rq we will
|
|
* post the final h_nr_running increment below.
|
|
*/
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
cfs_rq->h_nr_running++;
|
|
|
|
flags = ENQUEUE_WAKEUP;
|
|
}
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
cfs_rq->h_nr_running++;
|
|
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
|
|
update_cfs_shares(cfs_rq);
|
|
update_entity_load_avg(se, 1);
|
|
}
|
|
|
|
if (!se) {
|
|
update_rq_runnable_avg(rq, rq->nr_running);
|
|
inc_nr_running(rq);
|
|
}
|
|
hrtick_update(rq);
|
|
}
|
|
|
|
static void set_next_buddy(struct sched_entity *se);
|
|
|
|
/*
|
|
* The dequeue_task method is called before nr_running is
|
|
* decreased. We remove the task from the rbtree and
|
|
* update the fair scheduling stats:
|
|
*/
|
|
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se;
|
|
int task_sleep = flags & DEQUEUE_SLEEP;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
dequeue_entity(cfs_rq, se, flags);
|
|
|
|
/*
|
|
* end evaluation on encountering a throttled cfs_rq
|
|
*
|
|
* note: in the case of encountering a throttled cfs_rq we will
|
|
* post the final h_nr_running decrement below.
|
|
*/
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
cfs_rq->h_nr_running--;
|
|
|
|
/* Don't dequeue parent if it has other entities besides us */
|
|
if (cfs_rq->load.weight) {
|
|
/*
|
|
* Bias pick_next to pick a task from this cfs_rq, as
|
|
* p is sleeping when it is within its sched_slice.
|
|
*/
|
|
if (task_sleep && parent_entity(se))
|
|
set_next_buddy(parent_entity(se));
|
|
|
|
/* avoid re-evaluating load for this entity */
|
|
se = parent_entity(se);
|
|
break;
|
|
}
|
|
flags |= DEQUEUE_SLEEP;
|
|
}
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
cfs_rq->h_nr_running--;
|
|
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
|
|
update_cfs_shares(cfs_rq);
|
|
update_entity_load_avg(se, 1);
|
|
}
|
|
|
|
if (!se) {
|
|
dec_nr_running(rq);
|
|
update_rq_runnable_avg(rq, 1);
|
|
}
|
|
hrtick_update(rq);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/* Used instead of source_load when we know the type == 0 */
|
|
static unsigned long weighted_cpuload(const int cpu)
|
|
{
|
|
return cpu_rq(cpu)->cfs.runnable_load_avg;
|
|
}
|
|
|
|
/*
|
|
* Return a low guess at the load of a migration-source cpu weighted
|
|
* according to the scheduling class and "nice" value.
|
|
*
|
|
* We want to under-estimate the load of migration sources, to
|
|
* balance conservatively.
|
|
*/
|
|
static unsigned long source_load(int cpu, int type)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long total = weighted_cpuload(cpu);
|
|
|
|
if (type == 0 || !sched_feat(LB_BIAS))
|
|
return total;
|
|
|
|
return min(rq->cpu_load[type-1], total);
|
|
}
|
|
|
|
/*
|
|
* Return a high guess at the load of a migration-target cpu weighted
|
|
* according to the scheduling class and "nice" value.
|
|
*/
|
|
static unsigned long target_load(int cpu, int type)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long total = weighted_cpuload(cpu);
|
|
|
|
if (type == 0 || !sched_feat(LB_BIAS))
|
|
return total;
|
|
|
|
return max(rq->cpu_load[type-1], total);
|
|
}
|
|
|
|
static unsigned long power_of(int cpu)
|
|
{
|
|
return cpu_rq(cpu)->cpu_power;
|
|
}
|
|
|
|
static unsigned long cpu_avg_load_per_task(int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
|
|
unsigned long load_avg = rq->cfs.runnable_load_avg;
|
|
|
|
if (nr_running)
|
|
return load_avg / nr_running;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void record_wakee(struct task_struct *p)
|
|
{
|
|
/*
|
|
* Rough decay (wiping) for cost saving, don't worry
|
|
* about the boundary, really active task won't care
|
|
* about the loss.
|
|
*/
|
|
if (jiffies > current->wakee_flip_decay_ts + HZ) {
|
|
current->wakee_flips = 0;
|
|
current->wakee_flip_decay_ts = jiffies;
|
|
}
|
|
|
|
if (current->last_wakee != p) {
|
|
current->last_wakee = p;
|
|
current->wakee_flips++;
|
|
}
|
|
}
|
|
|
|
static void task_waking_fair(struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
u64 min_vruntime;
|
|
|
|
#ifndef CONFIG_64BIT
|
|
u64 min_vruntime_copy;
|
|
|
|
do {
|
|
min_vruntime_copy = cfs_rq->min_vruntime_copy;
|
|
smp_rmb();
|
|
min_vruntime = cfs_rq->min_vruntime;
|
|
} while (min_vruntime != min_vruntime_copy);
|
|
#else
|
|
min_vruntime = cfs_rq->min_vruntime;
|
|
#endif
|
|
|
|
se->vruntime -= min_vruntime;
|
|
record_wakee(p);
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
/*
|
|
* effective_load() calculates the load change as seen from the root_task_group
|
|
*
|
|
* Adding load to a group doesn't make a group heavier, but can cause movement
|
|
* of group shares between cpus. Assuming the shares were perfectly aligned one
|
|
* can calculate the shift in shares.
|
|
*
|
|
* Calculate the effective load difference if @wl is added (subtracted) to @tg
|
|
* on this @cpu and results in a total addition (subtraction) of @wg to the
|
|
* total group weight.
|
|
*
|
|
* Given a runqueue weight distribution (rw_i) we can compute a shares
|
|
* distribution (s_i) using:
|
|
*
|
|
* s_i = rw_i / \Sum rw_j (1)
|
|
*
|
|
* Suppose we have 4 CPUs and our @tg is a direct child of the root group and
|
|
* has 7 equal weight tasks, distributed as below (rw_i), with the resulting
|
|
* shares distribution (s_i):
|
|
*
|
|
* rw_i = { 2, 4, 1, 0 }
|
|
* s_i = { 2/7, 4/7, 1/7, 0 }
|
|
*
|
|
* As per wake_affine() we're interested in the load of two CPUs (the CPU the
|
|
* task used to run on and the CPU the waker is running on), we need to
|
|
* compute the effect of waking a task on either CPU and, in case of a sync
|
|
* wakeup, compute the effect of the current task going to sleep.
|
|
*
|
|
* So for a change of @wl to the local @cpu with an overall group weight change
|
|
* of @wl we can compute the new shares distribution (s'_i) using:
|
|
*
|
|
* s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
|
|
*
|
|
* Suppose we're interested in CPUs 0 and 1, and want to compute the load
|
|
* differences in waking a task to CPU 0. The additional task changes the
|
|
* weight and shares distributions like:
|
|
*
|
|
* rw'_i = { 3, 4, 1, 0 }
|
|
* s'_i = { 3/8, 4/8, 1/8, 0 }
|
|
*
|
|
* We can then compute the difference in effective weight by using:
|
|
*
|
|
* dw_i = S * (s'_i - s_i) (3)
|
|
*
|
|
* Where 'S' is the group weight as seen by its parent.
|
|
*
|
|
* Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
|
|
* times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
|
|
* 4/7) times the weight of the group.
|
|
*/
|
|
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
|
|
{
|
|
struct sched_entity *se = tg->se[cpu];
|
|
|
|
if (!tg->parent) /* the trivial, non-cgroup case */
|
|
return wl;
|
|
|
|
for_each_sched_entity(se) {
|
|
long w, W;
|
|
|
|
tg = se->my_q->tg;
|
|
|
|
/*
|
|
* W = @wg + \Sum rw_j
|
|
*/
|
|
W = wg + calc_tg_weight(tg, se->my_q);
|
|
|
|
/*
|
|
* w = rw_i + @wl
|
|
*/
|
|
w = se->my_q->load.weight + wl;
|
|
|
|
/*
|
|
* wl = S * s'_i; see (2)
|
|
*/
|
|
if (W > 0 && w < W)
|
|
wl = (w * tg->shares) / W;
|
|
else
|
|
wl = tg->shares;
|
|
|
|
/*
|
|
* Per the above, wl is the new se->load.weight value; since
|
|
* those are clipped to [MIN_SHARES, ...) do so now. See
|
|
* calc_cfs_shares().
|
|
*/
|
|
if (wl < MIN_SHARES)
|
|
wl = MIN_SHARES;
|
|
|
|
/*
|
|
* wl = dw_i = S * (s'_i - s_i); see (3)
|
|
*/
|
|
wl -= se->load.weight;
|
|
|
|
/*
|
|
* Recursively apply this logic to all parent groups to compute
|
|
* the final effective load change on the root group. Since
|
|
* only the @tg group gets extra weight, all parent groups can
|
|
* only redistribute existing shares. @wl is the shift in shares
|
|
* resulting from this level per the above.
|
|
*/
|
|
wg = 0;
|
|
}
|
|
|
|
return wl;
|
|
}
|
|
#else
|
|
|
|
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
|
|
{
|
|
return wl;
|
|
}
|
|
|
|
#endif
|
|
|
|
static int wake_wide(struct task_struct *p)
|
|
{
|
|
int factor = this_cpu_read(sd_llc_size);
|
|
|
|
/*
|
|
* Yeah, it's the switching-frequency, could means many wakee or
|
|
* rapidly switch, use factor here will just help to automatically
|
|
* adjust the loose-degree, so bigger node will lead to more pull.
|
|
*/
|
|
if (p->wakee_flips > factor) {
|
|
/*
|
|
* wakee is somewhat hot, it needs certain amount of cpu
|
|
* resource, so if waker is far more hot, prefer to leave
|
|
* it alone.
|
|
*/
|
|
if (current->wakee_flips > (factor * p->wakee_flips))
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
|
|
{
|
|
s64 this_load, load;
|
|
int idx, this_cpu, prev_cpu;
|
|
unsigned long tl_per_task;
|
|
struct task_group *tg;
|
|
unsigned long weight;
|
|
int balanced;
|
|
|
|
/*
|
|
* If we wake multiple tasks be careful to not bounce
|
|
* ourselves around too much.
|
|
*/
|
|
if (wake_wide(p))
|
|
return 0;
|
|
|
|
idx = sd->wake_idx;
|
|
this_cpu = smp_processor_id();
|
|
prev_cpu = task_cpu(p);
|
|
load = source_load(prev_cpu, idx);
|
|
this_load = target_load(this_cpu, idx);
|
|
|
|
/*
|
|
* If sync wakeup then subtract the (maximum possible)
|
|
* effect of the currently running task from the load
|
|
* of the current CPU:
|
|
*/
|
|
if (sync) {
|
|
tg = task_group(current);
|
|
weight = current->se.load.weight;
|
|
|
|
this_load += effective_load(tg, this_cpu, -weight, -weight);
|
|
load += effective_load(tg, prev_cpu, 0, -weight);
|
|
}
|
|
|
|
tg = task_group(p);
|
|
weight = p->se.load.weight;
|
|
|
|
/*
|
|
* In low-load situations, where prev_cpu is idle and this_cpu is idle
|
|
* due to the sync cause above having dropped this_load to 0, we'll
|
|
* always have an imbalance, but there's really nothing you can do
|
|
* about that, so that's good too.
|
|
*
|
|
* Otherwise check if either cpus are near enough in load to allow this
|
|
* task to be woken on this_cpu.
|
|
*/
|
|
if (this_load > 0) {
|
|
s64 this_eff_load, prev_eff_load;
|
|
|
|
this_eff_load = 100;
|
|
this_eff_load *= power_of(prev_cpu);
|
|
this_eff_load *= this_load +
|
|
effective_load(tg, this_cpu, weight, weight);
|
|
|
|
prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
|
|
prev_eff_load *= power_of(this_cpu);
|
|
prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
|
|
|
|
balanced = this_eff_load <= prev_eff_load;
|
|
} else
|
|
balanced = true;
|
|
|
|
/*
|
|
* If the currently running task will sleep within
|
|
* a reasonable amount of time then attract this newly
|
|
* woken task:
|
|
*/
|
|
if (sync && balanced)
|
|
return 1;
|
|
|
|
schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
|
|
tl_per_task = cpu_avg_load_per_task(this_cpu);
|
|
|
|
if (balanced ||
|
|
(this_load <= load &&
|
|
this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
|
|
/*
|
|
* This domain has SD_WAKE_AFFINE and
|
|
* p is cache cold in this domain, and
|
|
* there is no bad imbalance.
|
|
*/
|
|
schedstat_inc(sd, ttwu_move_affine);
|
|
schedstat_inc(p, se.statistics.nr_wakeups_affine);
|
|
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* find_idlest_group finds and returns the least busy CPU group within the
|
|
* domain.
|
|
*/
|
|
static struct sched_group *
|
|
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
|
|
int this_cpu, int load_idx)
|
|
{
|
|
struct sched_group *idlest = NULL, *group = sd->groups;
|
|
unsigned long min_load = ULONG_MAX, this_load = 0;
|
|
int imbalance = 100 + (sd->imbalance_pct-100)/2;
|
|
|
|
do {
|
|
unsigned long load, avg_load;
|
|
int local_group;
|
|
int i;
|
|
|
|
/* Skip over this group if it has no CPUs allowed */
|
|
if (!cpumask_intersects(sched_group_cpus(group),
|
|
tsk_cpus_allowed(p)))
|
|
continue;
|
|
|
|
local_group = cpumask_test_cpu(this_cpu,
|
|
sched_group_cpus(group));
|
|
|
|
/* Tally up the load of all CPUs in the group */
|
|
avg_load = 0;
|
|
|
|
for_each_cpu(i, sched_group_cpus(group)) {
|
|
/* Bias balancing toward cpus of our domain */
|
|
if (local_group)
|
|
load = source_load(i, load_idx);
|
|
else
|
|
load = target_load(i, load_idx);
|
|
|
|
avg_load += load;
|
|
}
|
|
|
|
/* Adjust by relative CPU power of the group */
|
|
avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
|
|
|
|
if (local_group) {
|
|
this_load = avg_load;
|
|
} else if (avg_load < min_load) {
|
|
min_load = avg_load;
|
|
idlest = group;
|
|
}
|
|
} while (group = group->next, group != sd->groups);
|
|
|
|
if (!idlest || 100*this_load < imbalance*min_load)
|
|
return NULL;
|
|
return idlest;
|
|
}
|
|
|
|
/*
|
|
* find_idlest_cpu - find the idlest cpu among the cpus in group.
|
|
*/
|
|
static int
|
|
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
|
|
{
|
|
unsigned long load, min_load = ULONG_MAX;
|
|
int idlest = -1;
|
|
int i;
|
|
|
|
/* Traverse only the allowed CPUs */
|
|
for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
|
|
load = weighted_cpuload(i);
|
|
|
|
if (load < min_load || (load == min_load && i == this_cpu)) {
|
|
min_load = load;
|
|
idlest = i;
|
|
}
|
|
}
|
|
|
|
return idlest;
|
|
}
|
|
|
|
/*
|
|
* Try and locate an idle CPU in the sched_domain.
|
|
*/
|
|
static int select_idle_sibling(struct task_struct *p, int target)
|
|
{
|
|
struct sched_domain *sd;
|
|
struct sched_group *sg;
|
|
int i = task_cpu(p);
|
|
|
|
if (idle_cpu(target))
|
|
return target;
|
|
|
|
/*
|
|
* If the prevous cpu is cache affine and idle, don't be stupid.
|
|
*/
|
|
if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
|
|
return i;
|
|
|
|
/*
|
|
* Otherwise, iterate the domains and find an elegible idle cpu.
|
|
*/
|
|
sd = rcu_dereference(per_cpu(sd_llc, target));
|
|
for_each_lower_domain(sd) {
|
|
sg = sd->groups;
|
|
do {
|
|
if (!cpumask_intersects(sched_group_cpus(sg),
|
|
tsk_cpus_allowed(p)))
|
|
goto next;
|
|
|
|
for_each_cpu(i, sched_group_cpus(sg)) {
|
|
if (i == target || !idle_cpu(i))
|
|
goto next;
|
|
}
|
|
|
|
target = cpumask_first_and(sched_group_cpus(sg),
|
|
tsk_cpus_allowed(p));
|
|
goto done;
|
|
next:
|
|
sg = sg->next;
|
|
} while (sg != sd->groups);
|
|
}
|
|
done:
|
|
return target;
|
|
}
|
|
|
|
/*
|
|
* sched_balance_self: balance the current task (running on cpu) in domains
|
|
* that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
|
|
* SD_BALANCE_EXEC.
|
|
*
|
|
* Balance, ie. select the least loaded group.
|
|
*
|
|
* Returns the target CPU number, or the same CPU if no balancing is needed.
|
|
*
|
|
* preempt must be disabled.
|
|
*/
|
|
static int
|
|
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
|
|
{
|
|
struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
|
|
int cpu = smp_processor_id();
|
|
int new_cpu = cpu;
|
|
int want_affine = 0;
|
|
int sync = wake_flags & WF_SYNC;
|
|
|
|
if (p->nr_cpus_allowed == 1)
|
|
return prev_cpu;
|
|
|
|
if (sd_flag & SD_BALANCE_WAKE) {
|
|
if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
|
|
want_affine = 1;
|
|
new_cpu = prev_cpu;
|
|
}
|
|
|
|
rcu_read_lock();
|
|
for_each_domain(cpu, tmp) {
|
|
if (!(tmp->flags & SD_LOAD_BALANCE))
|
|
continue;
|
|
|
|
/*
|
|
* If both cpu and prev_cpu are part of this domain,
|
|
* cpu is a valid SD_WAKE_AFFINE target.
|
|
*/
|
|
if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
|
|
cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
|
|
affine_sd = tmp;
|
|
break;
|
|
}
|
|
|
|
if (tmp->flags & sd_flag)
|
|
sd = tmp;
|
|
}
|
|
|
|
if (affine_sd) {
|
|
if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
|
|
prev_cpu = cpu;
|
|
|
|
new_cpu = select_idle_sibling(p, prev_cpu);
|
|
goto unlock;
|
|
}
|
|
|
|
while (sd) {
|
|
int load_idx = sd->forkexec_idx;
|
|
struct sched_group *group;
|
|
int weight;
|
|
|
|
if (!(sd->flags & sd_flag)) {
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
if (sd_flag & SD_BALANCE_WAKE)
|
|
load_idx = sd->wake_idx;
|
|
|
|
group = find_idlest_group(sd, p, cpu, load_idx);
|
|
if (!group) {
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
new_cpu = find_idlest_cpu(group, p, cpu);
|
|
if (new_cpu == -1 || new_cpu == cpu) {
|
|
/* Now try balancing at a lower domain level of cpu */
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
/* Now try balancing at a lower domain level of new_cpu */
|
|
cpu = new_cpu;
|
|
weight = sd->span_weight;
|
|
sd = NULL;
|
|
for_each_domain(cpu, tmp) {
|
|
if (weight <= tmp->span_weight)
|
|
break;
|
|
if (tmp->flags & sd_flag)
|
|
sd = tmp;
|
|
}
|
|
/* while loop will break here if sd == NULL */
|
|
}
|
|
unlock:
|
|
rcu_read_unlock();
|
|
|
|
return new_cpu;
|
|
}
|
|
|
|
/*
|
|
* Called immediately before a task is migrated to a new cpu; task_cpu(p) and
|
|
* cfs_rq_of(p) references at time of call are still valid and identify the
|
|
* previous cpu. However, the caller only guarantees p->pi_lock is held; no
|
|
* other assumptions, including the state of rq->lock, should be made.
|
|
*/
|
|
static void
|
|
migrate_task_rq_fair(struct task_struct *p, int next_cpu)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
/*
|
|
* Load tracking: accumulate removed load so that it can be processed
|
|
* when we next update owning cfs_rq under rq->lock. Tasks contribute
|
|
* to blocked load iff they have a positive decay-count. It can never
|
|
* be negative here since on-rq tasks have decay-count == 0.
|
|
*/
|
|
if (se->avg.decay_count) {
|
|
se->avg.decay_count = -__synchronize_entity_decay(se);
|
|
atomic_long_add(se->avg.load_avg_contrib,
|
|
&cfs_rq->removed_load);
|
|
}
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
static unsigned long
|
|
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
|
|
{
|
|
unsigned long gran = sysctl_sched_wakeup_granularity;
|
|
|
|
/*
|
|
* Since its curr running now, convert the gran from real-time
|
|
* to virtual-time in his units.
|
|
*
|
|
* By using 'se' instead of 'curr' we penalize light tasks, so
|
|
* they get preempted easier. That is, if 'se' < 'curr' then
|
|
* the resulting gran will be larger, therefore penalizing the
|
|
* lighter, if otoh 'se' > 'curr' then the resulting gran will
|
|
* be smaller, again penalizing the lighter task.
|
|
*
|
|
* This is especially important for buddies when the leftmost
|
|
* task is higher priority than the buddy.
|
|
*/
|
|
return calc_delta_fair(gran, se);
|
|
}
|
|
|
|
/*
|
|
* Should 'se' preempt 'curr'.
|
|
*
|
|
* |s1
|
|
* |s2
|
|
* |s3
|
|
* g
|
|
* |<--->|c
|
|
*
|
|
* w(c, s1) = -1
|
|
* w(c, s2) = 0
|
|
* w(c, s3) = 1
|
|
*
|
|
*/
|
|
static int
|
|
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
|
|
{
|
|
s64 gran, vdiff = curr->vruntime - se->vruntime;
|
|
|
|
if (vdiff <= 0)
|
|
return -1;
|
|
|
|
gran = wakeup_gran(curr, se);
|
|
if (vdiff > gran)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void set_last_buddy(struct sched_entity *se)
|
|
{
|
|
if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
|
|
return;
|
|
|
|
for_each_sched_entity(se)
|
|
cfs_rq_of(se)->last = se;
|
|
}
|
|
|
|
static void set_next_buddy(struct sched_entity *se)
|
|
{
|
|
if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
|
|
return;
|
|
|
|
for_each_sched_entity(se)
|
|
cfs_rq_of(se)->next = se;
|
|
}
|
|
|
|
static void set_skip_buddy(struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se)
|
|
cfs_rq_of(se)->skip = se;
|
|
}
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct sched_entity *se = &curr->se, *pse = &p->se;
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
int scale = cfs_rq->nr_running >= sched_nr_latency;
|
|
int next_buddy_marked = 0;
|
|
|
|
if (unlikely(se == pse))
|
|
return;
|
|
|
|
/*
|
|
* This is possible from callers such as move_task(), in which we
|
|
* unconditionally check_prempt_curr() after an enqueue (which may have
|
|
* lead to a throttle). This both saves work and prevents false
|
|
* next-buddy nomination below.
|
|
*/
|
|
if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
|
|
return;
|
|
|
|
if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
|
|
set_next_buddy(pse);
|
|
next_buddy_marked = 1;
|
|
}
|
|
|
|
/*
|
|
* We can come here with TIF_NEED_RESCHED already set from new task
|
|
* wake up path.
|
|
*
|
|
* Note: this also catches the edge-case of curr being in a throttled
|
|
* group (e.g. via set_curr_task), since update_curr() (in the
|
|
* enqueue of curr) will have resulted in resched being set. This
|
|
* prevents us from potentially nominating it as a false LAST_BUDDY
|
|
* below.
|
|
*/
|
|
if (test_tsk_need_resched(curr))
|
|
return;
|
|
|
|
/* Idle tasks are by definition preempted by non-idle tasks. */
|
|
if (unlikely(curr->policy == SCHED_IDLE) &&
|
|
likely(p->policy != SCHED_IDLE))
|
|
goto preempt;
|
|
|
|
/*
|
|
* Batch and idle tasks do not preempt non-idle tasks (their preemption
|
|
* is driven by the tick):
|
|
*/
|
|
if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
|
|
return;
|
|
|
|
find_matching_se(&se, &pse);
|
|
update_curr(cfs_rq_of(se));
|
|
BUG_ON(!pse);
|
|
if (wakeup_preempt_entity(se, pse) == 1) {
|
|
/*
|
|
* Bias pick_next to pick the sched entity that is
|
|
* triggering this preemption.
|
|
*/
|
|
if (!next_buddy_marked)
|
|
set_next_buddy(pse);
|
|
goto preempt;
|
|
}
|
|
|
|
return;
|
|
|
|
preempt:
|
|
resched_task(curr);
|
|
/*
|
|
* Only set the backward buddy when the current task is still
|
|
* on the rq. This can happen when a wakeup gets interleaved
|
|
* with schedule on the ->pre_schedule() or idle_balance()
|
|
* point, either of which can * drop the rq lock.
|
|
*
|
|
* Also, during early boot the idle thread is in the fair class,
|
|
* for obvious reasons its a bad idea to schedule back to it.
|
|
*/
|
|
if (unlikely(!se->on_rq || curr == rq->idle))
|
|
return;
|
|
|
|
if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
|
|
set_last_buddy(se);
|
|
}
|
|
|
|
static struct task_struct *pick_next_task_fair(struct rq *rq)
|
|
{
|
|
struct task_struct *p;
|
|
struct cfs_rq *cfs_rq = &rq->cfs;
|
|
struct sched_entity *se;
|
|
|
|
if (!cfs_rq->nr_running)
|
|
return NULL;
|
|
|
|
do {
|
|
se = pick_next_entity(cfs_rq);
|
|
set_next_entity(cfs_rq, se);
|
|
cfs_rq = group_cfs_rq(se);
|
|
} while (cfs_rq);
|
|
|
|
p = task_of(se);
|
|
if (hrtick_enabled(rq))
|
|
hrtick_start_fair(rq, p);
|
|
|
|
return p;
|
|
}
|
|
|
|
/*
|
|
* Account for a descheduled task:
|
|
*/
|
|
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
|
|
{
|
|
struct sched_entity *se = &prev->se;
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
put_prev_entity(cfs_rq, se);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* sched_yield() is very simple
|
|
*
|
|
* The magic of dealing with the ->skip buddy is in pick_next_entity.
|
|
*/
|
|
static void yield_task_fair(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
struct sched_entity *se = &curr->se;
|
|
|
|
/*
|
|
* Are we the only task in the tree?
|
|
*/
|
|
if (unlikely(rq->nr_running == 1))
|
|
return;
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
if (curr->policy != SCHED_BATCH) {
|
|
update_rq_clock(rq);
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
/*
|
|
* Tell update_rq_clock() that we've just updated,
|
|
* so we don't do microscopic update in schedule()
|
|
* and double the fastpath cost.
|
|
*/
|
|
rq->skip_clock_update = 1;
|
|
}
|
|
|
|
set_skip_buddy(se);
|
|
}
|
|
|
|
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
|
|
/* throttled hierarchies are not runnable */
|
|
if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
|
|
return false;
|
|
|
|
/* Tell the scheduler that we'd really like pse to run next. */
|
|
set_next_buddy(se);
|
|
|
|
yield_task_fair(rq);
|
|
|
|
return true;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/**************************************************
|
|
* Fair scheduling class load-balancing methods.
|
|
*
|
|
* BASICS
|
|
*
|
|
* The purpose of load-balancing is to achieve the same basic fairness the
|
|
* per-cpu scheduler provides, namely provide a proportional amount of compute
|
|
* time to each task. This is expressed in the following equation:
|
|
*
|
|
* W_i,n/P_i == W_j,n/P_j for all i,j (1)
|
|
*
|
|
* Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
|
|
* W_i,0 is defined as:
|
|
*
|
|
* W_i,0 = \Sum_j w_i,j (2)
|
|
*
|
|
* Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
|
|
* is derived from the nice value as per prio_to_weight[].
|
|
*
|
|
* The weight average is an exponential decay average of the instantaneous
|
|
* weight:
|
|
*
|
|
* W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
|
|
*
|
|
* P_i is the cpu power (or compute capacity) of cpu i, typically it is the
|
|
* fraction of 'recent' time available for SCHED_OTHER task execution. But it
|
|
* can also include other factors [XXX].
|
|
*
|
|
* To achieve this balance we define a measure of imbalance which follows
|
|
* directly from (1):
|
|
*
|
|
* imb_i,j = max{ avg(W/P), W_i/P_i } - min{ avg(W/P), W_j/P_j } (4)
|
|
*
|
|
* We them move tasks around to minimize the imbalance. In the continuous
|
|
* function space it is obvious this converges, in the discrete case we get
|
|
* a few fun cases generally called infeasible weight scenarios.
|
|
*
|
|
* [XXX expand on:
|
|
* - infeasible weights;
|
|
* - local vs global optima in the discrete case. ]
|
|
*
|
|
*
|
|
* SCHED DOMAINS
|
|
*
|
|
* In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
|
|
* for all i,j solution, we create a tree of cpus that follows the hardware
|
|
* topology where each level pairs two lower groups (or better). This results
|
|
* in O(log n) layers. Furthermore we reduce the number of cpus going up the
|
|
* tree to only the first of the previous level and we decrease the frequency
|
|
* of load-balance at each level inv. proportional to the number of cpus in
|
|
* the groups.
|
|
*
|
|
* This yields:
|
|
*
|
|
* log_2 n 1 n
|
|
* \Sum { --- * --- * 2^i } = O(n) (5)
|
|
* i = 0 2^i 2^i
|
|
* `- size of each group
|
|
* | | `- number of cpus doing load-balance
|
|
* | `- freq
|
|
* `- sum over all levels
|
|
*
|
|
* Coupled with a limit on how many tasks we can migrate every balance pass,
|
|
* this makes (5) the runtime complexity of the balancer.
|
|
*
|
|
* An important property here is that each CPU is still (indirectly) connected
|
|
* to every other cpu in at most O(log n) steps:
|
|
*
|
|
* The adjacency matrix of the resulting graph is given by:
|
|
*
|
|
* log_2 n
|
|
* A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
|
|
* k = 0
|
|
*
|
|
* And you'll find that:
|
|
*
|
|
* A^(log_2 n)_i,j != 0 for all i,j (7)
|
|
*
|
|
* Showing there's indeed a path between every cpu in at most O(log n) steps.
|
|
* The task movement gives a factor of O(m), giving a convergence complexity
|
|
* of:
|
|
*
|
|
* O(nm log n), n := nr_cpus, m := nr_tasks (8)
|
|
*
|
|
*
|
|
* WORK CONSERVING
|
|
*
|
|
* In order to avoid CPUs going idle while there's still work to do, new idle
|
|
* balancing is more aggressive and has the newly idle cpu iterate up the domain
|
|
* tree itself instead of relying on other CPUs to bring it work.
|
|
*
|
|
* This adds some complexity to both (5) and (8) but it reduces the total idle
|
|
* time.
|
|
*
|
|
* [XXX more?]
|
|
*
|
|
*
|
|
* CGROUPS
|
|
*
|
|
* Cgroups make a horror show out of (2), instead of a simple sum we get:
|
|
*
|
|
* s_k,i
|
|
* W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
|
|
* S_k
|
|
*
|
|
* Where
|
|
*
|
|
* s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
|
|
*
|
|
* w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
|
|
*
|
|
* The big problem is S_k, its a global sum needed to compute a local (W_i)
|
|
* property.
|
|
*
|
|
* [XXX write more on how we solve this.. _after_ merging pjt's patches that
|
|
* rewrite all of this once again.]
|
|
*/
|
|
|
|
static unsigned long __read_mostly max_load_balance_interval = HZ/10;
|
|
|
|
enum fbq_type { regular, remote, all };
|
|
|
|
#define LBF_ALL_PINNED 0x01
|
|
#define LBF_NEED_BREAK 0x02
|
|
#define LBF_DST_PINNED 0x04
|
|
#define LBF_SOME_PINNED 0x08
|
|
|
|
struct lb_env {
|
|
struct sched_domain *sd;
|
|
|
|
struct rq *src_rq;
|
|
int src_cpu;
|
|
|
|
int dst_cpu;
|
|
struct rq *dst_rq;
|
|
|
|
struct cpumask *dst_grpmask;
|
|
int new_dst_cpu;
|
|
enum cpu_idle_type idle;
|
|
long imbalance;
|
|
/* The set of CPUs under consideration for load-balancing */
|
|
struct cpumask *cpus;
|
|
|
|
unsigned int flags;
|
|
|
|
unsigned int loop;
|
|
unsigned int loop_break;
|
|
unsigned int loop_max;
|
|
|
|
enum fbq_type fbq_type;
|
|
};
|
|
|
|
/*
|
|
* move_task - move a task from one runqueue to another runqueue.
|
|
* Both runqueues must be locked.
|
|
*/
|
|
static void move_task(struct task_struct *p, struct lb_env *env)
|
|
{
|
|
deactivate_task(env->src_rq, p, 0);
|
|
set_task_cpu(p, env->dst_cpu);
|
|
activate_task(env->dst_rq, p, 0);
|
|
check_preempt_curr(env->dst_rq, p, 0);
|
|
}
|
|
|
|
/*
|
|
* Is this task likely cache-hot:
|
|
*/
|
|
static int
|
|
task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
|
|
{
|
|
s64 delta;
|
|
|
|
if (p->sched_class != &fair_sched_class)
|
|
return 0;
|
|
|
|
if (unlikely(p->policy == SCHED_IDLE))
|
|
return 0;
|
|
|
|
/*
|
|
* Buddy candidates are cache hot:
|
|
*/
|
|
if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
|
|
(&p->se == cfs_rq_of(&p->se)->next ||
|
|
&p->se == cfs_rq_of(&p->se)->last))
|
|
return 1;
|
|
|
|
if (sysctl_sched_migration_cost == -1)
|
|
return 1;
|
|
if (sysctl_sched_migration_cost == 0)
|
|
return 0;
|
|
|
|
delta = now - p->se.exec_start;
|
|
|
|
return delta < (s64)sysctl_sched_migration_cost;
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
/* Returns true if the destination node has incurred more faults */
|
|
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
|
|
{
|
|
int src_nid, dst_nid;
|
|
|
|
if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults ||
|
|
!(env->sd->flags & SD_NUMA)) {
|
|
return false;
|
|
}
|
|
|
|
src_nid = cpu_to_node(env->src_cpu);
|
|
dst_nid = cpu_to_node(env->dst_cpu);
|
|
|
|
if (src_nid == dst_nid)
|
|
return false;
|
|
|
|
/* Always encourage migration to the preferred node. */
|
|
if (dst_nid == p->numa_preferred_nid)
|
|
return true;
|
|
|
|
/* If both task and group weight improve, this move is a winner. */
|
|
if (task_weight(p, dst_nid) > task_weight(p, src_nid) &&
|
|
group_weight(p, dst_nid) > group_weight(p, src_nid))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
|
|
static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
|
|
{
|
|
int src_nid, dst_nid;
|
|
|
|
if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
|
|
return false;
|
|
|
|
if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
|
|
return false;
|
|
|
|
src_nid = cpu_to_node(env->src_cpu);
|
|
dst_nid = cpu_to_node(env->dst_cpu);
|
|
|
|
if (src_nid == dst_nid)
|
|
return false;
|
|
|
|
/* Migrating away from the preferred node is always bad. */
|
|
if (src_nid == p->numa_preferred_nid)
|
|
return true;
|
|
|
|
/* If either task or group weight get worse, don't do it. */
|
|
if (task_weight(p, dst_nid) < task_weight(p, src_nid) ||
|
|
group_weight(p, dst_nid) < group_weight(p, src_nid))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
#else
|
|
static inline bool migrate_improves_locality(struct task_struct *p,
|
|
struct lb_env *env)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static inline bool migrate_degrades_locality(struct task_struct *p,
|
|
struct lb_env *env)
|
|
{
|
|
return false;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
|
|
*/
|
|
static
|
|
int can_migrate_task(struct task_struct *p, struct lb_env *env)
|
|
{
|
|
int tsk_cache_hot = 0;
|
|
/*
|
|
* We do not migrate tasks that are:
|
|
* 1) throttled_lb_pair, or
|
|
* 2) cannot be migrated to this CPU due to cpus_allowed, or
|
|
* 3) running (obviously), or
|
|
* 4) are cache-hot on their current CPU.
|
|
*/
|
|
if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
|
|
return 0;
|
|
|
|
if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
|
|
int cpu;
|
|
|
|
schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
|
|
|
|
env->flags |= LBF_SOME_PINNED;
|
|
|
|
/*
|
|
* Remember if this task can be migrated to any other cpu in
|
|
* our sched_group. We may want to revisit it if we couldn't
|
|
* meet load balance goals by pulling other tasks on src_cpu.
|
|
*
|
|
* Also avoid computing new_dst_cpu if we have already computed
|
|
* one in current iteration.
|
|
*/
|
|
if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
|
|
return 0;
|
|
|
|
/* Prevent to re-select dst_cpu via env's cpus */
|
|
for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
|
|
if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
|
|
env->flags |= LBF_DST_PINNED;
|
|
env->new_dst_cpu = cpu;
|
|
break;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Record that we found atleast one task that could run on dst_cpu */
|
|
env->flags &= ~LBF_ALL_PINNED;
|
|
|
|
if (task_running(env->src_rq, p)) {
|
|
schedstat_inc(p, se.statistics.nr_failed_migrations_running);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Aggressive migration if:
|
|
* 1) destination numa is preferred
|
|
* 2) task is cache cold, or
|
|
* 3) too many balance attempts have failed.
|
|
*/
|
|
tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
|
|
if (!tsk_cache_hot)
|
|
tsk_cache_hot = migrate_degrades_locality(p, env);
|
|
|
|
if (migrate_improves_locality(p, env)) {
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
if (tsk_cache_hot) {
|
|
schedstat_inc(env->sd, lb_hot_gained[env->idle]);
|
|
schedstat_inc(p, se.statistics.nr_forced_migrations);
|
|
}
|
|
#endif
|
|
return 1;
|
|
}
|
|
|
|
if (!tsk_cache_hot ||
|
|
env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
|
|
|
|
if (tsk_cache_hot) {
|
|
schedstat_inc(env->sd, lb_hot_gained[env->idle]);
|
|
schedstat_inc(p, se.statistics.nr_forced_migrations);
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
|
|
schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* move_one_task tries to move exactly one task from busiest to this_rq, as
|
|
* part of active balancing operations within "domain".
|
|
* Returns 1 if successful and 0 otherwise.
|
|
*
|
|
* Called with both runqueues locked.
|
|
*/
|
|
static int move_one_task(struct lb_env *env)
|
|
{
|
|
struct task_struct *p, *n;
|
|
|
|
list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
|
|
if (!can_migrate_task(p, env))
|
|
continue;
|
|
|
|
move_task(p, env);
|
|
/*
|
|
* Right now, this is only the second place move_task()
|
|
* is called, so we can safely collect move_task()
|
|
* stats here rather than inside move_task().
|
|
*/
|
|
schedstat_inc(env->sd, lb_gained[env->idle]);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static const unsigned int sched_nr_migrate_break = 32;
|
|
|
|
/*
|
|
* move_tasks tries to move up to imbalance weighted load from busiest to
|
|
* this_rq, as part of a balancing operation within domain "sd".
|
|
* Returns 1 if successful and 0 otherwise.
|
|
*
|
|
* Called with both runqueues locked.
|
|
*/
|
|
static int move_tasks(struct lb_env *env)
|
|
{
|
|
struct list_head *tasks = &env->src_rq->cfs_tasks;
|
|
struct task_struct *p;
|
|
unsigned long load;
|
|
int pulled = 0;
|
|
|
|
if (env->imbalance <= 0)
|
|
return 0;
|
|
|
|
while (!list_empty(tasks)) {
|
|
p = list_first_entry(tasks, struct task_struct, se.group_node);
|
|
|
|
env->loop++;
|
|
/* We've more or less seen every task there is, call it quits */
|
|
if (env->loop > env->loop_max)
|
|
break;
|
|
|
|
/* take a breather every nr_migrate tasks */
|
|
if (env->loop > env->loop_break) {
|
|
env->loop_break += sched_nr_migrate_break;
|
|
env->flags |= LBF_NEED_BREAK;
|
|
break;
|
|
}
|
|
|
|
if (!can_migrate_task(p, env))
|
|
goto next;
|
|
|
|
load = task_h_load(p);
|
|
|
|
if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
|
|
goto next;
|
|
|
|
if ((load / 2) > env->imbalance)
|
|
goto next;
|
|
|
|
move_task(p, env);
|
|
pulled++;
|
|
env->imbalance -= load;
|
|
|
|
#ifdef CONFIG_PREEMPT
|
|
/*
|
|
* NEWIDLE balancing is a source of latency, so preemptible
|
|
* kernels will stop after the first task is pulled to minimize
|
|
* the critical section.
|
|
*/
|
|
if (env->idle == CPU_NEWLY_IDLE)
|
|
break;
|
|
#endif
|
|
|
|
/*
|
|
* We only want to steal up to the prescribed amount of
|
|
* weighted load.
|
|
*/
|
|
if (env->imbalance <= 0)
|
|
break;
|
|
|
|
continue;
|
|
next:
|
|
list_move_tail(&p->se.group_node, tasks);
|
|
}
|
|
|
|
/*
|
|
* Right now, this is one of only two places move_task() is called,
|
|
* so we can safely collect move_task() stats here rather than
|
|
* inside move_task().
|
|
*/
|
|
schedstat_add(env->sd, lb_gained[env->idle], pulled);
|
|
|
|
return pulled;
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
/*
|
|
* update tg->load_weight by folding this cpu's load_avg
|
|
*/
|
|
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
|
|
{
|
|
struct sched_entity *se = tg->se[cpu];
|
|
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
|
|
|
|
/* throttled entities do not contribute to load */
|
|
if (throttled_hierarchy(cfs_rq))
|
|
return;
|
|
|
|
update_cfs_rq_blocked_load(cfs_rq, 1);
|
|
|
|
if (se) {
|
|
update_entity_load_avg(se, 1);
|
|
/*
|
|
* We pivot on our runnable average having decayed to zero for
|
|
* list removal. This generally implies that all our children
|
|
* have also been removed (modulo rounding error or bandwidth
|
|
* control); however, such cases are rare and we can fix these
|
|
* at enqueue.
|
|
*
|
|
* TODO: fix up out-of-order children on enqueue.
|
|
*/
|
|
if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
|
|
list_del_leaf_cfs_rq(cfs_rq);
|
|
} else {
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
update_rq_runnable_avg(rq, rq->nr_running);
|
|
}
|
|
}
|
|
|
|
static void update_blocked_averages(int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
struct cfs_rq *cfs_rq;
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&rq->lock, flags);
|
|
update_rq_clock(rq);
|
|
/*
|
|
* Iterates the task_group tree in a bottom up fashion, see
|
|
* list_add_leaf_cfs_rq() for details.
|
|
*/
|
|
for_each_leaf_cfs_rq(rq, cfs_rq) {
|
|
/*
|
|
* Note: We may want to consider periodically releasing
|
|
* rq->lock about these updates so that creating many task
|
|
* groups does not result in continually extending hold time.
|
|
*/
|
|
__update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
|
|
}
|
|
|
|
raw_spin_unlock_irqrestore(&rq->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Compute the hierarchical load factor for cfs_rq and all its ascendants.
|
|
* This needs to be done in a top-down fashion because the load of a child
|
|
* group is a fraction of its parents load.
|
|
*/
|
|
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
|
|
unsigned long now = jiffies;
|
|
unsigned long load;
|
|
|
|
if (cfs_rq->last_h_load_update == now)
|
|
return;
|
|
|
|
cfs_rq->h_load_next = NULL;
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
cfs_rq->h_load_next = se;
|
|
if (cfs_rq->last_h_load_update == now)
|
|
break;
|
|
}
|
|
|
|
if (!se) {
|
|
cfs_rq->h_load = cfs_rq->runnable_load_avg;
|
|
cfs_rq->last_h_load_update = now;
|
|
}
|
|
|
|
while ((se = cfs_rq->h_load_next) != NULL) {
|
|
load = cfs_rq->h_load;
|
|
load = div64_ul(load * se->avg.load_avg_contrib,
|
|
cfs_rq->runnable_load_avg + 1);
|
|
cfs_rq = group_cfs_rq(se);
|
|
cfs_rq->h_load = load;
|
|
cfs_rq->last_h_load_update = now;
|
|
}
|
|
}
|
|
|
|
static unsigned long task_h_load(struct task_struct *p)
|
|
{
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(p);
|
|
|
|
update_cfs_rq_h_load(cfs_rq);
|
|
return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
|
|
cfs_rq->runnable_load_avg + 1);
|
|
}
|
|
#else
|
|
static inline void update_blocked_averages(int cpu)
|
|
{
|
|
}
|
|
|
|
static unsigned long task_h_load(struct task_struct *p)
|
|
{
|
|
return p->se.avg.load_avg_contrib;
|
|
}
|
|
#endif
|
|
|
|
/********** Helpers for find_busiest_group ************************/
|
|
/*
|
|
* sg_lb_stats - stats of a sched_group required for load_balancing
|
|
*/
|
|
struct sg_lb_stats {
|
|
unsigned long avg_load; /*Avg load across the CPUs of the group */
|
|
unsigned long group_load; /* Total load over the CPUs of the group */
|
|
unsigned long sum_weighted_load; /* Weighted load of group's tasks */
|
|
unsigned long load_per_task;
|
|
unsigned long group_power;
|
|
unsigned int sum_nr_running; /* Nr tasks running in the group */
|
|
unsigned int group_capacity;
|
|
unsigned int idle_cpus;
|
|
unsigned int group_weight;
|
|
int group_imb; /* Is there an imbalance in the group ? */
|
|
int group_has_capacity; /* Is there extra capacity in the group? */
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
unsigned int nr_numa_running;
|
|
unsigned int nr_preferred_running;
|
|
#endif
|
|
};
|
|
|
|
/*
|
|
* sd_lb_stats - Structure to store the statistics of a sched_domain
|
|
* during load balancing.
|
|
*/
|
|
struct sd_lb_stats {
|
|
struct sched_group *busiest; /* Busiest group in this sd */
|
|
struct sched_group *local; /* Local group in this sd */
|
|
unsigned long total_load; /* Total load of all groups in sd */
|
|
unsigned long total_pwr; /* Total power of all groups in sd */
|
|
unsigned long avg_load; /* Average load across all groups in sd */
|
|
|
|
struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
|
|
struct sg_lb_stats local_stat; /* Statistics of the local group */
|
|
};
|
|
|
|
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
|
|
{
|
|
/*
|
|
* Skimp on the clearing to avoid duplicate work. We can avoid clearing
|
|
* local_stat because update_sg_lb_stats() does a full clear/assignment.
|
|
* We must however clear busiest_stat::avg_load because
|
|
* update_sd_pick_busiest() reads this before assignment.
|
|
*/
|
|
*sds = (struct sd_lb_stats){
|
|
.busiest = NULL,
|
|
.local = NULL,
|
|
.total_load = 0UL,
|
|
.total_pwr = 0UL,
|
|
.busiest_stat = {
|
|
.avg_load = 0UL,
|
|
},
|
|
};
|
|
}
|
|
|
|
/**
|
|
* get_sd_load_idx - Obtain the load index for a given sched domain.
|
|
* @sd: The sched_domain whose load_idx is to be obtained.
|
|
* @idle: The idle status of the CPU for whose sd load_idx is obtained.
|
|
*
|
|
* Return: The load index.
|
|
*/
|
|
static inline int get_sd_load_idx(struct sched_domain *sd,
|
|
enum cpu_idle_type idle)
|
|
{
|
|
int load_idx;
|
|
|
|
switch (idle) {
|
|
case CPU_NOT_IDLE:
|
|
load_idx = sd->busy_idx;
|
|
break;
|
|
|
|
case CPU_NEWLY_IDLE:
|
|
load_idx = sd->newidle_idx;
|
|
break;
|
|
default:
|
|
load_idx = sd->idle_idx;
|
|
break;
|
|
}
|
|
|
|
return load_idx;
|
|
}
|
|
|
|
static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
return SCHED_POWER_SCALE;
|
|
}
|
|
|
|
unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
return default_scale_freq_power(sd, cpu);
|
|
}
|
|
|
|
static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
unsigned long weight = sd->span_weight;
|
|
unsigned long smt_gain = sd->smt_gain;
|
|
|
|
smt_gain /= weight;
|
|
|
|
return smt_gain;
|
|
}
|
|
|
|
unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
return default_scale_smt_power(sd, cpu);
|
|
}
|
|
|
|
static unsigned long scale_rt_power(int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
u64 total, available, age_stamp, avg;
|
|
|
|
/*
|
|
* Since we're reading these variables without serialization make sure
|
|
* we read them once before doing sanity checks on them.
|
|
*/
|
|
age_stamp = ACCESS_ONCE(rq->age_stamp);
|
|
avg = ACCESS_ONCE(rq->rt_avg);
|
|
|
|
total = sched_avg_period() + (rq_clock(rq) - age_stamp);
|
|
|
|
if (unlikely(total < avg)) {
|
|
/* Ensures that power won't end up being negative */
|
|
available = 0;
|
|
} else {
|
|
available = total - avg;
|
|
}
|
|
|
|
if (unlikely((s64)total < SCHED_POWER_SCALE))
|
|
total = SCHED_POWER_SCALE;
|
|
|
|
total >>= SCHED_POWER_SHIFT;
|
|
|
|
return div_u64(available, total);
|
|
}
|
|
|
|
static void update_cpu_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
unsigned long weight = sd->span_weight;
|
|
unsigned long power = SCHED_POWER_SCALE;
|
|
struct sched_group *sdg = sd->groups;
|
|
|
|
if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
|
|
if (sched_feat(ARCH_POWER))
|
|
power *= arch_scale_smt_power(sd, cpu);
|
|
else
|
|
power *= default_scale_smt_power(sd, cpu);
|
|
|
|
power >>= SCHED_POWER_SHIFT;
|
|
}
|
|
|
|
sdg->sgp->power_orig = power;
|
|
|
|
if (sched_feat(ARCH_POWER))
|
|
power *= arch_scale_freq_power(sd, cpu);
|
|
else
|
|
power *= default_scale_freq_power(sd, cpu);
|
|
|
|
power >>= SCHED_POWER_SHIFT;
|
|
|
|
power *= scale_rt_power(cpu);
|
|
power >>= SCHED_POWER_SHIFT;
|
|
|
|
if (!power)
|
|
power = 1;
|
|
|
|
cpu_rq(cpu)->cpu_power = power;
|
|
sdg->sgp->power = power;
|
|
}
|
|
|
|
void update_group_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
struct sched_domain *child = sd->child;
|
|
struct sched_group *group, *sdg = sd->groups;
|
|
unsigned long power, power_orig;
|
|
unsigned long interval;
|
|
|
|
interval = msecs_to_jiffies(sd->balance_interval);
|
|
interval = clamp(interval, 1UL, max_load_balance_interval);
|
|
sdg->sgp->next_update = jiffies + interval;
|
|
|
|
if (!child) {
|
|
update_cpu_power(sd, cpu);
|
|
return;
|
|
}
|
|
|
|
power_orig = power = 0;
|
|
|
|
if (child->flags & SD_OVERLAP) {
|
|
/*
|
|
* SD_OVERLAP domains cannot assume that child groups
|
|
* span the current group.
|
|
*/
|
|
|
|
for_each_cpu(cpu, sched_group_cpus(sdg)) {
|
|
struct sched_group_power *sgp;
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
/*
|
|
* build_sched_domains() -> init_sched_groups_power()
|
|
* gets here before we've attached the domains to the
|
|
* runqueues.
|
|
*
|
|
* Use power_of(), which is set irrespective of domains
|
|
* in update_cpu_power().
|
|
*
|
|
* This avoids power/power_orig from being 0 and
|
|
* causing divide-by-zero issues on boot.
|
|
*
|
|
* Runtime updates will correct power_orig.
|
|
*/
|
|
if (unlikely(!rq->sd)) {
|
|
power_orig += power_of(cpu);
|
|
power += power_of(cpu);
|
|
continue;
|
|
}
|
|
|
|
sgp = rq->sd->groups->sgp;
|
|
power_orig += sgp->power_orig;
|
|
power += sgp->power;
|
|
}
|
|
} else {
|
|
/*
|
|
* !SD_OVERLAP domains can assume that child groups
|
|
* span the current group.
|
|
*/
|
|
|
|
group = child->groups;
|
|
do {
|
|
power_orig += group->sgp->power_orig;
|
|
power += group->sgp->power;
|
|
group = group->next;
|
|
} while (group != child->groups);
|
|
}
|
|
|
|
sdg->sgp->power_orig = power_orig;
|
|
sdg->sgp->power = power;
|
|
}
|
|
|
|
/*
|
|
* Try and fix up capacity for tiny siblings, this is needed when
|
|
* things like SD_ASYM_PACKING need f_b_g to select another sibling
|
|
* which on its own isn't powerful enough.
|
|
*
|
|
* See update_sd_pick_busiest() and check_asym_packing().
|
|
*/
|
|
static inline int
|
|
fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
|
|
{
|
|
/*
|
|
* Only siblings can have significantly less than SCHED_POWER_SCALE
|
|
*/
|
|
if (!(sd->flags & SD_SHARE_CPUPOWER))
|
|
return 0;
|
|
|
|
/*
|
|
* If ~90% of the cpu_power is still there, we're good.
|
|
*/
|
|
if (group->sgp->power * 32 > group->sgp->power_orig * 29)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Group imbalance indicates (and tries to solve) the problem where balancing
|
|
* groups is inadequate due to tsk_cpus_allowed() constraints.
|
|
*
|
|
* Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
|
|
* cpumask covering 1 cpu of the first group and 3 cpus of the second group.
|
|
* Something like:
|
|
*
|
|
* { 0 1 2 3 } { 4 5 6 7 }
|
|
* * * * *
|
|
*
|
|
* If we were to balance group-wise we'd place two tasks in the first group and
|
|
* two tasks in the second group. Clearly this is undesired as it will overload
|
|
* cpu 3 and leave one of the cpus in the second group unused.
|
|
*
|
|
* The current solution to this issue is detecting the skew in the first group
|
|
* by noticing the lower domain failed to reach balance and had difficulty
|
|
* moving tasks due to affinity constraints.
|
|
*
|
|
* When this is so detected; this group becomes a candidate for busiest; see
|
|
* update_sd_pick_busiest(). And calculate_imbalance() and
|
|
* find_busiest_group() avoid some of the usual balance conditions to allow it
|
|
* to create an effective group imbalance.
|
|
*
|
|
* This is a somewhat tricky proposition since the next run might not find the
|
|
* group imbalance and decide the groups need to be balanced again. A most
|
|
* subtle and fragile situation.
|
|
*/
|
|
|
|
static inline int sg_imbalanced(struct sched_group *group)
|
|
{
|
|
return group->sgp->imbalance;
|
|
}
|
|
|
|
/*
|
|
* Compute the group capacity.
|
|
*
|
|
* Avoid the issue where N*frac(smt_power) >= 1 creates 'phantom' cores by
|
|
* first dividing out the smt factor and computing the actual number of cores
|
|
* and limit power unit capacity with that.
|
|
*/
|
|
static inline int sg_capacity(struct lb_env *env, struct sched_group *group)
|
|
{
|
|
unsigned int capacity, smt, cpus;
|
|
unsigned int power, power_orig;
|
|
|
|
power = group->sgp->power;
|
|
power_orig = group->sgp->power_orig;
|
|
cpus = group->group_weight;
|
|
|
|
/* smt := ceil(cpus / power), assumes: 1 < smt_power < 2 */
|
|
smt = DIV_ROUND_UP(SCHED_POWER_SCALE * cpus, power_orig);
|
|
capacity = cpus / smt; /* cores */
|
|
|
|
capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE));
|
|
if (!capacity)
|
|
capacity = fix_small_capacity(env->sd, group);
|
|
|
|
return capacity;
|
|
}
|
|
|
|
/**
|
|
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
|
|
* @env: The load balancing environment.
|
|
* @group: sched_group whose statistics are to be updated.
|
|
* @load_idx: Load index of sched_domain of this_cpu for load calc.
|
|
* @local_group: Does group contain this_cpu.
|
|
* @sgs: variable to hold the statistics for this group.
|
|
*/
|
|
static inline void update_sg_lb_stats(struct lb_env *env,
|
|
struct sched_group *group, int load_idx,
|
|
int local_group, struct sg_lb_stats *sgs)
|
|
{
|
|
unsigned long nr_running;
|
|
unsigned long load;
|
|
int i;
|
|
|
|
memset(sgs, 0, sizeof(*sgs));
|
|
|
|
for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
|
|
struct rq *rq = cpu_rq(i);
|
|
|
|
nr_running = rq->nr_running;
|
|
|
|
/* Bias balancing toward cpus of our domain */
|
|
if (local_group)
|
|
load = target_load(i, load_idx);
|
|
else
|
|
load = source_load(i, load_idx);
|
|
|
|
sgs->group_load += load;
|
|
sgs->sum_nr_running += nr_running;
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
sgs->nr_numa_running += rq->nr_numa_running;
|
|
sgs->nr_preferred_running += rq->nr_preferred_running;
|
|
#endif
|
|
sgs->sum_weighted_load += weighted_cpuload(i);
|
|
if (idle_cpu(i))
|
|
sgs->idle_cpus++;
|
|
}
|
|
|
|
/* Adjust by relative CPU power of the group */
|
|
sgs->group_power = group->sgp->power;
|
|
sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / sgs->group_power;
|
|
|
|
if (sgs->sum_nr_running)
|
|
sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
|
|
|
|
sgs->group_weight = group->group_weight;
|
|
|
|
sgs->group_imb = sg_imbalanced(group);
|
|
sgs->group_capacity = sg_capacity(env, group);
|
|
|
|
if (sgs->group_capacity > sgs->sum_nr_running)
|
|
sgs->group_has_capacity = 1;
|
|
}
|
|
|
|
/**
|
|
* update_sd_pick_busiest - return 1 on busiest group
|
|
* @env: The load balancing environment.
|
|
* @sds: sched_domain statistics
|
|
* @sg: sched_group candidate to be checked for being the busiest
|
|
* @sgs: sched_group statistics
|
|
*
|
|
* Determine if @sg is a busier group than the previously selected
|
|
* busiest group.
|
|
*
|
|
* Return: %true if @sg is a busier group than the previously selected
|
|
* busiest group. %false otherwise.
|
|
*/
|
|
static bool update_sd_pick_busiest(struct lb_env *env,
|
|
struct sd_lb_stats *sds,
|
|
struct sched_group *sg,
|
|
struct sg_lb_stats *sgs)
|
|
{
|
|
if (sgs->avg_load <= sds->busiest_stat.avg_load)
|
|
return false;
|
|
|
|
if (sgs->sum_nr_running > sgs->group_capacity)
|
|
return true;
|
|
|
|
if (sgs->group_imb)
|
|
return true;
|
|
|
|
/*
|
|
* ASYM_PACKING needs to move all the work to the lowest
|
|
* numbered CPUs in the group, therefore mark all groups
|
|
* higher than ourself as busy.
|
|
*/
|
|
if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
|
|
env->dst_cpu < group_first_cpu(sg)) {
|
|
if (!sds->busiest)
|
|
return true;
|
|
|
|
if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
|
|
{
|
|
if (sgs->sum_nr_running > sgs->nr_numa_running)
|
|
return regular;
|
|
if (sgs->sum_nr_running > sgs->nr_preferred_running)
|
|
return remote;
|
|
return all;
|
|
}
|
|
|
|
static inline enum fbq_type fbq_classify_rq(struct rq *rq)
|
|
{
|
|
if (rq->nr_running > rq->nr_numa_running)
|
|
return regular;
|
|
if (rq->nr_running > rq->nr_preferred_running)
|
|
return remote;
|
|
return all;
|
|
}
|
|
#else
|
|
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
|
|
{
|
|
return all;
|
|
}
|
|
|
|
static inline enum fbq_type fbq_classify_rq(struct rq *rq)
|
|
{
|
|
return regular;
|
|
}
|
|
#endif /* CONFIG_NUMA_BALANCING */
|
|
|
|
/**
|
|
* update_sd_lb_stats - Update sched_domain's statistics for load balancing.
|
|
* @env: The load balancing environment.
|
|
* @sds: variable to hold the statistics for this sched_domain.
|
|
*/
|
|
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
|
|
{
|
|
struct sched_domain *child = env->sd->child;
|
|
struct sched_group *sg = env->sd->groups;
|
|
struct sg_lb_stats tmp_sgs;
|
|
int load_idx, prefer_sibling = 0;
|
|
|
|
if (child && child->flags & SD_PREFER_SIBLING)
|
|
prefer_sibling = 1;
|
|
|
|
load_idx = get_sd_load_idx(env->sd, env->idle);
|
|
|
|
do {
|
|
struct sg_lb_stats *sgs = &tmp_sgs;
|
|
int local_group;
|
|
|
|
local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
|
|
if (local_group) {
|
|
sds->local = sg;
|
|
sgs = &sds->local_stat;
|
|
|
|
if (env->idle != CPU_NEWLY_IDLE ||
|
|
time_after_eq(jiffies, sg->sgp->next_update))
|
|
update_group_power(env->sd, env->dst_cpu);
|
|
}
|
|
|
|
update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
|
|
|
|
if (local_group)
|
|
goto next_group;
|
|
|
|
/*
|
|
* In case the child domain prefers tasks go to siblings
|
|
* first, lower the sg capacity to one so that we'll try
|
|
* and move all the excess tasks away. We lower the capacity
|
|
* of a group only if the local group has the capacity to fit
|
|
* these excess tasks, i.e. nr_running < group_capacity. The
|
|
* extra check prevents the case where you always pull from the
|
|
* heaviest group when it is already under-utilized (possible
|
|
* with a large weight task outweighs the tasks on the system).
|
|
*/
|
|
if (prefer_sibling && sds->local &&
|
|
sds->local_stat.group_has_capacity)
|
|
sgs->group_capacity = min(sgs->group_capacity, 1U);
|
|
|
|
if (update_sd_pick_busiest(env, sds, sg, sgs)) {
|
|
sds->busiest = sg;
|
|
sds->busiest_stat = *sgs;
|
|
}
|
|
|
|
next_group:
|
|
/* Now, start updating sd_lb_stats */
|
|
sds->total_load += sgs->group_load;
|
|
sds->total_pwr += sgs->group_power;
|
|
|
|
sg = sg->next;
|
|
} while (sg != env->sd->groups);
|
|
|
|
if (env->sd->flags & SD_NUMA)
|
|
env->fbq_type = fbq_classify_group(&sds->busiest_stat);
|
|
}
|
|
|
|
/**
|
|
* check_asym_packing - Check to see if the group is packed into the
|
|
* sched doman.
|
|
*
|
|
* This is primarily intended to used at the sibling level. Some
|
|
* cores like POWER7 prefer to use lower numbered SMT threads. In the
|
|
* case of POWER7, it can move to lower SMT modes only when higher
|
|
* threads are idle. When in lower SMT modes, the threads will
|
|
* perform better since they share less core resources. Hence when we
|
|
* have idle threads, we want them to be the higher ones.
|
|
*
|
|
* This packing function is run on idle threads. It checks to see if
|
|
* the busiest CPU in this domain (core in the P7 case) has a higher
|
|
* CPU number than the packing function is being run on. Here we are
|
|
* assuming lower CPU number will be equivalent to lower a SMT thread
|
|
* number.
|
|
*
|
|
* Return: 1 when packing is required and a task should be moved to
|
|
* this CPU. The amount of the imbalance is returned in *imbalance.
|
|
*
|
|
* @env: The load balancing environment.
|
|
* @sds: Statistics of the sched_domain which is to be packed
|
|
*/
|
|
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
|
|
{
|
|
int busiest_cpu;
|
|
|
|
if (!(env->sd->flags & SD_ASYM_PACKING))
|
|
return 0;
|
|
|
|
if (!sds->busiest)
|
|
return 0;
|
|
|
|
busiest_cpu = group_first_cpu(sds->busiest);
|
|
if (env->dst_cpu > busiest_cpu)
|
|
return 0;
|
|
|
|
env->imbalance = DIV_ROUND_CLOSEST(
|
|
sds->busiest_stat.avg_load * sds->busiest_stat.group_power,
|
|
SCHED_POWER_SCALE);
|
|
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* fix_small_imbalance - Calculate the minor imbalance that exists
|
|
* amongst the groups of a sched_domain, during
|
|
* load balancing.
|
|
* @env: The load balancing environment.
|
|
* @sds: Statistics of the sched_domain whose imbalance is to be calculated.
|
|
*/
|
|
static inline
|
|
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
|
|
{
|
|
unsigned long tmp, pwr_now = 0, pwr_move = 0;
|
|
unsigned int imbn = 2;
|
|
unsigned long scaled_busy_load_per_task;
|
|
struct sg_lb_stats *local, *busiest;
|
|
|
|
local = &sds->local_stat;
|
|
busiest = &sds->busiest_stat;
|
|
|
|
if (!local->sum_nr_running)
|
|
local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
|
|
else if (busiest->load_per_task > local->load_per_task)
|
|
imbn = 1;
|
|
|
|
scaled_busy_load_per_task =
|
|
(busiest->load_per_task * SCHED_POWER_SCALE) /
|
|
busiest->group_power;
|
|
|
|
if (busiest->avg_load + scaled_busy_load_per_task >=
|
|
local->avg_load + (scaled_busy_load_per_task * imbn)) {
|
|
env->imbalance = busiest->load_per_task;
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* OK, we don't have enough imbalance to justify moving tasks,
|
|
* however we may be able to increase total CPU power used by
|
|
* moving them.
|
|
*/
|
|
|
|
pwr_now += busiest->group_power *
|
|
min(busiest->load_per_task, busiest->avg_load);
|
|
pwr_now += local->group_power *
|
|
min(local->load_per_task, local->avg_load);
|
|
pwr_now /= SCHED_POWER_SCALE;
|
|
|
|
/* Amount of load we'd subtract */
|
|
tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
|
|
busiest->group_power;
|
|
if (busiest->avg_load > tmp) {
|
|
pwr_move += busiest->group_power *
|
|
min(busiest->load_per_task,
|
|
busiest->avg_load - tmp);
|
|
}
|
|
|
|
/* Amount of load we'd add */
|
|
if (busiest->avg_load * busiest->group_power <
|
|
busiest->load_per_task * SCHED_POWER_SCALE) {
|
|
tmp = (busiest->avg_load * busiest->group_power) /
|
|
local->group_power;
|
|
} else {
|
|
tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
|
|
local->group_power;
|
|
}
|
|
pwr_move += local->group_power *
|
|
min(local->load_per_task, local->avg_load + tmp);
|
|
pwr_move /= SCHED_POWER_SCALE;
|
|
|
|
/* Move if we gain throughput */
|
|
if (pwr_move > pwr_now)
|
|
env->imbalance = busiest->load_per_task;
|
|
}
|
|
|
|
/**
|
|
* calculate_imbalance - Calculate the amount of imbalance present within the
|
|
* groups of a given sched_domain during load balance.
|
|
* @env: load balance environment
|
|
* @sds: statistics of the sched_domain whose imbalance is to be calculated.
|
|
*/
|
|
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
|
|
{
|
|
unsigned long max_pull, load_above_capacity = ~0UL;
|
|
struct sg_lb_stats *local, *busiest;
|
|
|
|
local = &sds->local_stat;
|
|
busiest = &sds->busiest_stat;
|
|
|
|
if (busiest->group_imb) {
|
|
/*
|
|
* In the group_imb case we cannot rely on group-wide averages
|
|
* to ensure cpu-load equilibrium, look at wider averages. XXX
|
|
*/
|
|
busiest->load_per_task =
|
|
min(busiest->load_per_task, sds->avg_load);
|
|
}
|
|
|
|
/*
|
|
* In the presence of smp nice balancing, certain scenarios can have
|
|
* max load less than avg load(as we skip the groups at or below
|
|
* its cpu_power, while calculating max_load..)
|
|
*/
|
|
if (busiest->avg_load <= sds->avg_load ||
|
|
local->avg_load >= sds->avg_load) {
|
|
env->imbalance = 0;
|
|
return fix_small_imbalance(env, sds);
|
|
}
|
|
|
|
if (!busiest->group_imb) {
|
|
/*
|
|
* Don't want to pull so many tasks that a group would go idle.
|
|
* Except of course for the group_imb case, since then we might
|
|
* have to drop below capacity to reach cpu-load equilibrium.
|
|
*/
|
|
load_above_capacity =
|
|
(busiest->sum_nr_running - busiest->group_capacity);
|
|
|
|
load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
|
|
load_above_capacity /= busiest->group_power;
|
|
}
|
|
|
|
/*
|
|
* We're trying to get all the cpus to the average_load, so we don't
|
|
* want to push ourselves above the average load, nor do we wish to
|
|
* reduce the max loaded cpu below the average load. At the same time,
|
|
* we also don't want to reduce the group load below the group capacity
|
|
* (so that we can implement power-savings policies etc). Thus we look
|
|
* for the minimum possible imbalance.
|
|
*/
|
|
max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
|
|
|
|
/* How much load to actually move to equalise the imbalance */
|
|
env->imbalance = min(
|
|
max_pull * busiest->group_power,
|
|
(sds->avg_load - local->avg_load) * local->group_power
|
|
) / SCHED_POWER_SCALE;
|
|
|
|
/*
|
|
* if *imbalance is less than the average load per runnable task
|
|
* there is no guarantee that any tasks will be moved so we'll have
|
|
* a think about bumping its value to force at least one task to be
|
|
* moved
|
|
*/
|
|
if (env->imbalance < busiest->load_per_task)
|
|
return fix_small_imbalance(env, sds);
|
|
}
|
|
|
|
/******* find_busiest_group() helpers end here *********************/
|
|
|
|
/**
|
|
* find_busiest_group - Returns the busiest group within the sched_domain
|
|
* if there is an imbalance. If there isn't an imbalance, and
|
|
* the user has opted for power-savings, it returns a group whose
|
|
* CPUs can be put to idle by rebalancing those tasks elsewhere, if
|
|
* such a group exists.
|
|
*
|
|
* Also calculates the amount of weighted load which should be moved
|
|
* to restore balance.
|
|
*
|
|
* @env: The load balancing environment.
|
|
*
|
|
* Return: - The busiest group if imbalance exists.
|
|
* - If no imbalance and user has opted for power-savings balance,
|
|
* return the least loaded group whose CPUs can be
|
|
* put to idle by rebalancing its tasks onto our group.
|
|
*/
|
|
static struct sched_group *find_busiest_group(struct lb_env *env)
|
|
{
|
|
struct sg_lb_stats *local, *busiest;
|
|
struct sd_lb_stats sds;
|
|
|
|
init_sd_lb_stats(&sds);
|
|
|
|
/*
|
|
* Compute the various statistics relavent for load balancing at
|
|
* this level.
|
|
*/
|
|
update_sd_lb_stats(env, &sds);
|
|
local = &sds.local_stat;
|
|
busiest = &sds.busiest_stat;
|
|
|
|
if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
|
|
check_asym_packing(env, &sds))
|
|
return sds.busiest;
|
|
|
|
/* There is no busy sibling group to pull tasks from */
|
|
if (!sds.busiest || busiest->sum_nr_running == 0)
|
|
goto out_balanced;
|
|
|
|
sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
|
|
|
|
/*
|
|
* If the busiest group is imbalanced the below checks don't
|
|
* work because they assume all things are equal, which typically
|
|
* isn't true due to cpus_allowed constraints and the like.
|
|
*/
|
|
if (busiest->group_imb)
|
|
goto force_balance;
|
|
|
|
/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
|
|
if (env->idle == CPU_NEWLY_IDLE && local->group_has_capacity &&
|
|
!busiest->group_has_capacity)
|
|
goto force_balance;
|
|
|
|
/*
|
|
* If the local group is more busy than the selected busiest group
|
|
* don't try and pull any tasks.
|
|
*/
|
|
if (local->avg_load >= busiest->avg_load)
|
|
goto out_balanced;
|
|
|
|
/*
|
|
* Don't pull any tasks if this group is already above the domain
|
|
* average load.
|
|
*/
|
|
if (local->avg_load >= sds.avg_load)
|
|
goto out_balanced;
|
|
|
|
if (env->idle == CPU_IDLE) {
|
|
/*
|
|
* This cpu is idle. If the busiest group load doesn't
|
|
* have more tasks than the number of available cpu's and
|
|
* there is no imbalance between this and busiest group
|
|
* wrt to idle cpu's, it is balanced.
|
|
*/
|
|
if ((local->idle_cpus < busiest->idle_cpus) &&
|
|
busiest->sum_nr_running <= busiest->group_weight)
|
|
goto out_balanced;
|
|
} else {
|
|
/*
|
|
* In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
|
|
* imbalance_pct to be conservative.
|
|
*/
|
|
if (100 * busiest->avg_load <=
|
|
env->sd->imbalance_pct * local->avg_load)
|
|
goto out_balanced;
|
|
}
|
|
|
|
force_balance:
|
|
/* Looks like there is an imbalance. Compute it */
|
|
calculate_imbalance(env, &sds);
|
|
return sds.busiest;
|
|
|
|
out_balanced:
|
|
env->imbalance = 0;
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* find_busiest_queue - find the busiest runqueue among the cpus in group.
|
|
*/
|
|
static struct rq *find_busiest_queue(struct lb_env *env,
|
|
struct sched_group *group)
|
|
{
|
|
struct rq *busiest = NULL, *rq;
|
|
unsigned long busiest_load = 0, busiest_power = 1;
|
|
int i;
|
|
|
|
for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
|
|
unsigned long power, capacity, wl;
|
|
enum fbq_type rt;
|
|
|
|
rq = cpu_rq(i);
|
|
rt = fbq_classify_rq(rq);
|
|
|
|
/*
|
|
* We classify groups/runqueues into three groups:
|
|
* - regular: there are !numa tasks
|
|
* - remote: there are numa tasks that run on the 'wrong' node
|
|
* - all: there is no distinction
|
|
*
|
|
* In order to avoid migrating ideally placed numa tasks,
|
|
* ignore those when there's better options.
|
|
*
|
|
* If we ignore the actual busiest queue to migrate another
|
|
* task, the next balance pass can still reduce the busiest
|
|
* queue by moving tasks around inside the node.
|
|
*
|
|
* If we cannot move enough load due to this classification
|
|
* the next pass will adjust the group classification and
|
|
* allow migration of more tasks.
|
|
*
|
|
* Both cases only affect the total convergence complexity.
|
|
*/
|
|
if (rt > env->fbq_type)
|
|
continue;
|
|
|
|
power = power_of(i);
|
|
capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE);
|
|
if (!capacity)
|
|
capacity = fix_small_capacity(env->sd, group);
|
|
|
|
wl = weighted_cpuload(i);
|
|
|
|
/*
|
|
* When comparing with imbalance, use weighted_cpuload()
|
|
* which is not scaled with the cpu power.
|
|
*/
|
|
if (capacity && rq->nr_running == 1 && wl > env->imbalance)
|
|
continue;
|
|
|
|
/*
|
|
* For the load comparisons with the other cpu's, consider
|
|
* the weighted_cpuload() scaled with the cpu power, so that
|
|
* the load can be moved away from the cpu that is potentially
|
|
* running at a lower capacity.
|
|
*
|
|
* Thus we're looking for max(wl_i / power_i), crosswise
|
|
* multiplication to rid ourselves of the division works out
|
|
* to: wl_i * power_j > wl_j * power_i; where j is our
|
|
* previous maximum.
|
|
*/
|
|
if (wl * busiest_power > busiest_load * power) {
|
|
busiest_load = wl;
|
|
busiest_power = power;
|
|
busiest = rq;
|
|
}
|
|
}
|
|
|
|
return busiest;
|
|
}
|
|
|
|
/*
|
|
* Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
|
|
* so long as it is large enough.
|
|
*/
|
|
#define MAX_PINNED_INTERVAL 512
|
|
|
|
/* Working cpumask for load_balance and load_balance_newidle. */
|
|
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
|
|
|
|
static int need_active_balance(struct lb_env *env)
|
|
{
|
|
struct sched_domain *sd = env->sd;
|
|
|
|
if (env->idle == CPU_NEWLY_IDLE) {
|
|
|
|
/*
|
|
* ASYM_PACKING needs to force migrate tasks from busy but
|
|
* higher numbered CPUs in order to pack all tasks in the
|
|
* lowest numbered CPUs.
|
|
*/
|
|
if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
|
|
return 1;
|
|
}
|
|
|
|
return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
|
|
}
|
|
|
|
static int active_load_balance_cpu_stop(void *data);
|
|
|
|
static int should_we_balance(struct lb_env *env)
|
|
{
|
|
struct sched_group *sg = env->sd->groups;
|
|
struct cpumask *sg_cpus, *sg_mask;
|
|
int cpu, balance_cpu = -1;
|
|
|
|
/*
|
|
* In the newly idle case, we will allow all the cpu's
|
|
* to do the newly idle load balance.
|
|
*/
|
|
if (env->idle == CPU_NEWLY_IDLE)
|
|
return 1;
|
|
|
|
sg_cpus = sched_group_cpus(sg);
|
|
sg_mask = sched_group_mask(sg);
|
|
/* Try to find first idle cpu */
|
|
for_each_cpu_and(cpu, sg_cpus, env->cpus) {
|
|
if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
|
|
continue;
|
|
|
|
balance_cpu = cpu;
|
|
break;
|
|
}
|
|
|
|
if (balance_cpu == -1)
|
|
balance_cpu = group_balance_cpu(sg);
|
|
|
|
/*
|
|
* First idle cpu or the first cpu(busiest) in this sched group
|
|
* is eligible for doing load balancing at this and above domains.
|
|
*/
|
|
return balance_cpu == env->dst_cpu;
|
|
}
|
|
|
|
/*
|
|
* Check this_cpu to ensure it is balanced within domain. Attempt to move
|
|
* tasks if there is an imbalance.
|
|
*/
|
|
static int load_balance(int this_cpu, struct rq *this_rq,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *continue_balancing)
|
|
{
|
|
int ld_moved, cur_ld_moved, active_balance = 0;
|
|
struct sched_domain *sd_parent = sd->parent;
|
|
struct sched_group *group;
|
|
struct rq *busiest;
|
|
unsigned long flags;
|
|
struct cpumask *cpus = __get_cpu_var(load_balance_mask);
|
|
|
|
struct lb_env env = {
|
|
.sd = sd,
|
|
.dst_cpu = this_cpu,
|
|
.dst_rq = this_rq,
|
|
.dst_grpmask = sched_group_cpus(sd->groups),
|
|
.idle = idle,
|
|
.loop_break = sched_nr_migrate_break,
|
|
.cpus = cpus,
|
|
.fbq_type = all,
|
|
};
|
|
|
|
/*
|
|
* For NEWLY_IDLE load_balancing, we don't need to consider
|
|
* other cpus in our group
|
|
*/
|
|
if (idle == CPU_NEWLY_IDLE)
|
|
env.dst_grpmask = NULL;
|
|
|
|
cpumask_copy(cpus, cpu_active_mask);
|
|
|
|
schedstat_inc(sd, lb_count[idle]);
|
|
|
|
redo:
|
|
if (!should_we_balance(&env)) {
|
|
*continue_balancing = 0;
|
|
goto out_balanced;
|
|
}
|
|
|
|
group = find_busiest_group(&env);
|
|
if (!group) {
|
|
schedstat_inc(sd, lb_nobusyg[idle]);
|
|
goto out_balanced;
|
|
}
|
|
|
|
busiest = find_busiest_queue(&env, group);
|
|
if (!busiest) {
|
|
schedstat_inc(sd, lb_nobusyq[idle]);
|
|
goto out_balanced;
|
|
}
|
|
|
|
BUG_ON(busiest == env.dst_rq);
|
|
|
|
schedstat_add(sd, lb_imbalance[idle], env.imbalance);
|
|
|
|
ld_moved = 0;
|
|
if (busiest->nr_running > 1) {
|
|
/*
|
|
* Attempt to move tasks. If find_busiest_group has found
|
|
* an imbalance but busiest->nr_running <= 1, the group is
|
|
* still unbalanced. ld_moved simply stays zero, so it is
|
|
* correctly treated as an imbalance.
|
|
*/
|
|
env.flags |= LBF_ALL_PINNED;
|
|
env.src_cpu = busiest->cpu;
|
|
env.src_rq = busiest;
|
|
env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
|
|
|
|
more_balance:
|
|
local_irq_save(flags);
|
|
double_rq_lock(env.dst_rq, busiest);
|
|
|
|
/*
|
|
* cur_ld_moved - load moved in current iteration
|
|
* ld_moved - cumulative load moved across iterations
|
|
*/
|
|
cur_ld_moved = move_tasks(&env);
|
|
ld_moved += cur_ld_moved;
|
|
double_rq_unlock(env.dst_rq, busiest);
|
|
local_irq_restore(flags);
|
|
|
|
/*
|
|
* some other cpu did the load balance for us.
|
|
*/
|
|
if (cur_ld_moved && env.dst_cpu != smp_processor_id())
|
|
resched_cpu(env.dst_cpu);
|
|
|
|
if (env.flags & LBF_NEED_BREAK) {
|
|
env.flags &= ~LBF_NEED_BREAK;
|
|
goto more_balance;
|
|
}
|
|
|
|
/*
|
|
* Revisit (affine) tasks on src_cpu that couldn't be moved to
|
|
* us and move them to an alternate dst_cpu in our sched_group
|
|
* where they can run. The upper limit on how many times we
|
|
* iterate on same src_cpu is dependent on number of cpus in our
|
|
* sched_group.
|
|
*
|
|
* This changes load balance semantics a bit on who can move
|
|
* load to a given_cpu. In addition to the given_cpu itself
|
|
* (or a ilb_cpu acting on its behalf where given_cpu is
|
|
* nohz-idle), we now have balance_cpu in a position to move
|
|
* load to given_cpu. In rare situations, this may cause
|
|
* conflicts (balance_cpu and given_cpu/ilb_cpu deciding
|
|
* _independently_ and at _same_ time to move some load to
|
|
* given_cpu) causing exceess load to be moved to given_cpu.
|
|
* This however should not happen so much in practice and
|
|
* moreover subsequent load balance cycles should correct the
|
|
* excess load moved.
|
|
*/
|
|
if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
|
|
|
|
/* Prevent to re-select dst_cpu via env's cpus */
|
|
cpumask_clear_cpu(env.dst_cpu, env.cpus);
|
|
|
|
env.dst_rq = cpu_rq(env.new_dst_cpu);
|
|
env.dst_cpu = env.new_dst_cpu;
|
|
env.flags &= ~LBF_DST_PINNED;
|
|
env.loop = 0;
|
|
env.loop_break = sched_nr_migrate_break;
|
|
|
|
/*
|
|
* Go back to "more_balance" rather than "redo" since we
|
|
* need to continue with same src_cpu.
|
|
*/
|
|
goto more_balance;
|
|
}
|
|
|
|
/*
|
|
* We failed to reach balance because of affinity.
|
|
*/
|
|
if (sd_parent) {
|
|
int *group_imbalance = &sd_parent->groups->sgp->imbalance;
|
|
|
|
if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
|
|
*group_imbalance = 1;
|
|
} else if (*group_imbalance)
|
|
*group_imbalance = 0;
|
|
}
|
|
|
|
/* All tasks on this runqueue were pinned by CPU affinity */
|
|
if (unlikely(env.flags & LBF_ALL_PINNED)) {
|
|
cpumask_clear_cpu(cpu_of(busiest), cpus);
|
|
if (!cpumask_empty(cpus)) {
|
|
env.loop = 0;
|
|
env.loop_break = sched_nr_migrate_break;
|
|
goto redo;
|
|
}
|
|
goto out_balanced;
|
|
}
|
|
}
|
|
|
|
if (!ld_moved) {
|
|
schedstat_inc(sd, lb_failed[idle]);
|
|
/*
|
|
* Increment the failure counter only on periodic balance.
|
|
* We do not want newidle balance, which can be very
|
|
* frequent, pollute the failure counter causing
|
|
* excessive cache_hot migrations and active balances.
|
|
*/
|
|
if (idle != CPU_NEWLY_IDLE)
|
|
sd->nr_balance_failed++;
|
|
|
|
if (need_active_balance(&env)) {
|
|
raw_spin_lock_irqsave(&busiest->lock, flags);
|
|
|
|
/* don't kick the active_load_balance_cpu_stop,
|
|
* if the curr task on busiest cpu can't be
|
|
* moved to this_cpu
|
|
*/
|
|
if (!cpumask_test_cpu(this_cpu,
|
|
tsk_cpus_allowed(busiest->curr))) {
|
|
raw_spin_unlock_irqrestore(&busiest->lock,
|
|
flags);
|
|
env.flags |= LBF_ALL_PINNED;
|
|
goto out_one_pinned;
|
|
}
|
|
|
|
/*
|
|
* ->active_balance synchronizes accesses to
|
|
* ->active_balance_work. Once set, it's cleared
|
|
* only after active load balance is finished.
|
|
*/
|
|
if (!busiest->active_balance) {
|
|
busiest->active_balance = 1;
|
|
busiest->push_cpu = this_cpu;
|
|
active_balance = 1;
|
|
}
|
|
raw_spin_unlock_irqrestore(&busiest->lock, flags);
|
|
|
|
if (active_balance) {
|
|
stop_one_cpu_nowait(cpu_of(busiest),
|
|
active_load_balance_cpu_stop, busiest,
|
|
&busiest->active_balance_work);
|
|
}
|
|
|
|
/*
|
|
* We've kicked active balancing, reset the failure
|
|
* counter.
|
|
*/
|
|
sd->nr_balance_failed = sd->cache_nice_tries+1;
|
|
}
|
|
} else
|
|
sd->nr_balance_failed = 0;
|
|
|
|
if (likely(!active_balance)) {
|
|
/* We were unbalanced, so reset the balancing interval */
|
|
sd->balance_interval = sd->min_interval;
|
|
} else {
|
|
/*
|
|
* If we've begun active balancing, start to back off. This
|
|
* case may not be covered by the all_pinned logic if there
|
|
* is only 1 task on the busy runqueue (because we don't call
|
|
* move_tasks).
|
|
*/
|
|
if (sd->balance_interval < sd->max_interval)
|
|
sd->balance_interval *= 2;
|
|
}
|
|
|
|
goto out;
|
|
|
|
out_balanced:
|
|
schedstat_inc(sd, lb_balanced[idle]);
|
|
|
|
sd->nr_balance_failed = 0;
|
|
|
|
out_one_pinned:
|
|
/* tune up the balancing interval */
|
|
if (((env.flags & LBF_ALL_PINNED) &&
|
|
sd->balance_interval < MAX_PINNED_INTERVAL) ||
|
|
(sd->balance_interval < sd->max_interval))
|
|
sd->balance_interval *= 2;
|
|
|
|
ld_moved = 0;
|
|
out:
|
|
return ld_moved;
|
|
}
|
|
|
|
/*
|
|
* idle_balance is called by schedule() if this_cpu is about to become
|
|
* idle. Attempts to pull tasks from other CPUs.
|
|
*/
|
|
void idle_balance(int this_cpu, struct rq *this_rq)
|
|
{
|
|
struct sched_domain *sd;
|
|
int pulled_task = 0;
|
|
unsigned long next_balance = jiffies + HZ;
|
|
u64 curr_cost = 0;
|
|
|
|
this_rq->idle_stamp = rq_clock(this_rq);
|
|
|
|
if (this_rq->avg_idle < sysctl_sched_migration_cost)
|
|
return;
|
|
|
|
/*
|
|
* Drop the rq->lock, but keep IRQ/preempt disabled.
|
|
*/
|
|
raw_spin_unlock(&this_rq->lock);
|
|
|
|
update_blocked_averages(this_cpu);
|
|
rcu_read_lock();
|
|
for_each_domain(this_cpu, sd) {
|
|
unsigned long interval;
|
|
int continue_balancing = 1;
|
|
u64 t0, domain_cost;
|
|
|
|
if (!(sd->flags & SD_LOAD_BALANCE))
|
|
continue;
|
|
|
|
if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
|
|
break;
|
|
|
|
if (sd->flags & SD_BALANCE_NEWIDLE) {
|
|
t0 = sched_clock_cpu(this_cpu);
|
|
|
|
/* If we've pulled tasks over stop searching: */
|
|
pulled_task = load_balance(this_cpu, this_rq,
|
|
sd, CPU_NEWLY_IDLE,
|
|
&continue_balancing);
|
|
|
|
domain_cost = sched_clock_cpu(this_cpu) - t0;
|
|
if (domain_cost > sd->max_newidle_lb_cost)
|
|
sd->max_newidle_lb_cost = domain_cost;
|
|
|
|
curr_cost += domain_cost;
|
|
}
|
|
|
|
interval = msecs_to_jiffies(sd->balance_interval);
|
|
if (time_after(next_balance, sd->last_balance + interval))
|
|
next_balance = sd->last_balance + interval;
|
|
if (pulled_task) {
|
|
this_rq->idle_stamp = 0;
|
|
break;
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
raw_spin_lock(&this_rq->lock);
|
|
|
|
if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
|
|
/*
|
|
* We are going idle. next_balance may be set based on
|
|
* a busy processor. So reset next_balance.
|
|
*/
|
|
this_rq->next_balance = next_balance;
|
|
}
|
|
|
|
if (curr_cost > this_rq->max_idle_balance_cost)
|
|
this_rq->max_idle_balance_cost = curr_cost;
|
|
}
|
|
|
|
/*
|
|
* active_load_balance_cpu_stop is run by cpu stopper. It pushes
|
|
* running tasks off the busiest CPU onto idle CPUs. It requires at
|
|
* least 1 task to be running on each physical CPU where possible, and
|
|
* avoids physical / logical imbalances.
|
|
*/
|
|
static int active_load_balance_cpu_stop(void *data)
|
|
{
|
|
struct rq *busiest_rq = data;
|
|
int busiest_cpu = cpu_of(busiest_rq);
|
|
int target_cpu = busiest_rq->push_cpu;
|
|
struct rq *target_rq = cpu_rq(target_cpu);
|
|
struct sched_domain *sd;
|
|
|
|
raw_spin_lock_irq(&busiest_rq->lock);
|
|
|
|
/* make sure the requested cpu hasn't gone down in the meantime */
|
|
if (unlikely(busiest_cpu != smp_processor_id() ||
|
|
!busiest_rq->active_balance))
|
|
goto out_unlock;
|
|
|
|
/* Is there any task to move? */
|
|
if (busiest_rq->nr_running <= 1)
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* This condition is "impossible", if it occurs
|
|
* we need to fix it. Originally reported by
|
|
* Bjorn Helgaas on a 128-cpu setup.
|
|
*/
|
|
BUG_ON(busiest_rq == target_rq);
|
|
|
|
/* move a task from busiest_rq to target_rq */
|
|
double_lock_balance(busiest_rq, target_rq);
|
|
|
|
/* Search for an sd spanning us and the target CPU. */
|
|
rcu_read_lock();
|
|
for_each_domain(target_cpu, sd) {
|
|
if ((sd->flags & SD_LOAD_BALANCE) &&
|
|
cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
|
|
break;
|
|
}
|
|
|
|
if (likely(sd)) {
|
|
struct lb_env env = {
|
|
.sd = sd,
|
|
.dst_cpu = target_cpu,
|
|
.dst_rq = target_rq,
|
|
.src_cpu = busiest_rq->cpu,
|
|
.src_rq = busiest_rq,
|
|
.idle = CPU_IDLE,
|
|
};
|
|
|
|
schedstat_inc(sd, alb_count);
|
|
|
|
if (move_one_task(&env))
|
|
schedstat_inc(sd, alb_pushed);
|
|
else
|
|
schedstat_inc(sd, alb_failed);
|
|
}
|
|
rcu_read_unlock();
|
|
double_unlock_balance(busiest_rq, target_rq);
|
|
out_unlock:
|
|
busiest_rq->active_balance = 0;
|
|
raw_spin_unlock_irq(&busiest_rq->lock);
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
/*
|
|
* idle load balancing details
|
|
* - When one of the busy CPUs notice that there may be an idle rebalancing
|
|
* needed, they will kick the idle load balancer, which then does idle
|
|
* load balancing for all the idle CPUs.
|
|
*/
|
|
static struct {
|
|
cpumask_var_t idle_cpus_mask;
|
|
atomic_t nr_cpus;
|
|
unsigned long next_balance; /* in jiffy units */
|
|
} nohz ____cacheline_aligned;
|
|
|
|
static inline int find_new_ilb(int call_cpu)
|
|
{
|
|
int ilb = cpumask_first(nohz.idle_cpus_mask);
|
|
|
|
if (ilb < nr_cpu_ids && idle_cpu(ilb))
|
|
return ilb;
|
|
|
|
return nr_cpu_ids;
|
|
}
|
|
|
|
/*
|
|
* Kick a CPU to do the nohz balancing, if it is time for it. We pick the
|
|
* nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
|
|
* CPU (if there is one).
|
|
*/
|
|
static void nohz_balancer_kick(int cpu)
|
|
{
|
|
int ilb_cpu;
|
|
|
|
nohz.next_balance++;
|
|
|
|
ilb_cpu = find_new_ilb(cpu);
|
|
|
|
if (ilb_cpu >= nr_cpu_ids)
|
|
return;
|
|
|
|
if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
|
|
return;
|
|
/*
|
|
* Use smp_send_reschedule() instead of resched_cpu().
|
|
* This way we generate a sched IPI on the target cpu which
|
|
* is idle. And the softirq performing nohz idle load balance
|
|
* will be run before returning from the IPI.
|
|
*/
|
|
smp_send_reschedule(ilb_cpu);
|
|
return;
|
|
}
|
|
|
|
static inline void nohz_balance_exit_idle(int cpu)
|
|
{
|
|
if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
|
|
cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
|
|
atomic_dec(&nohz.nr_cpus);
|
|
clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
|
|
}
|
|
}
|
|
|
|
static inline void set_cpu_sd_state_busy(void)
|
|
{
|
|
struct sched_domain *sd;
|
|
int cpu = smp_processor_id();
|
|
|
|
rcu_read_lock();
|
|
sd = rcu_dereference(per_cpu(sd_busy, cpu));
|
|
|
|
if (!sd || !sd->nohz_idle)
|
|
goto unlock;
|
|
sd->nohz_idle = 0;
|
|
|
|
atomic_inc(&sd->groups->sgp->nr_busy_cpus);
|
|
unlock:
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
void set_cpu_sd_state_idle(void)
|
|
{
|
|
struct sched_domain *sd;
|
|
int cpu = smp_processor_id();
|
|
|
|
rcu_read_lock();
|
|
sd = rcu_dereference(per_cpu(sd_busy, cpu));
|
|
|
|
if (!sd || sd->nohz_idle)
|
|
goto unlock;
|
|
sd->nohz_idle = 1;
|
|
|
|
atomic_dec(&sd->groups->sgp->nr_busy_cpus);
|
|
unlock:
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/*
|
|
* This routine will record that the cpu is going idle with tick stopped.
|
|
* This info will be used in performing idle load balancing in the future.
|
|
*/
|
|
void nohz_balance_enter_idle(int cpu)
|
|
{
|
|
/*
|
|
* If this cpu is going down, then nothing needs to be done.
|
|
*/
|
|
if (!cpu_active(cpu))
|
|
return;
|
|
|
|
if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
|
|
return;
|
|
|
|
cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
|
|
atomic_inc(&nohz.nr_cpus);
|
|
set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
|
|
}
|
|
|
|
static int sched_ilb_notifier(struct notifier_block *nfb,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
switch (action & ~CPU_TASKS_FROZEN) {
|
|
case CPU_DYING:
|
|
nohz_balance_exit_idle(smp_processor_id());
|
|
return NOTIFY_OK;
|
|
default:
|
|
return NOTIFY_DONE;
|
|
}
|
|
}
|
|
#endif
|
|
|
|
static DEFINE_SPINLOCK(balancing);
|
|
|
|
/*
|
|
* Scale the max load_balance interval with the number of CPUs in the system.
|
|
* This trades load-balance latency on larger machines for less cross talk.
|
|
*/
|
|
void update_max_interval(void)
|
|
{
|
|
max_load_balance_interval = HZ*num_online_cpus()/10;
|
|
}
|
|
|
|
/*
|
|
* It checks each scheduling domain to see if it is due to be balanced,
|
|
* and initiates a balancing operation if so.
|
|
*
|
|
* Balancing parameters are set up in init_sched_domains.
|
|
*/
|
|
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
|
|
{
|
|
int continue_balancing = 1;
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long interval;
|
|
struct sched_domain *sd;
|
|
/* Earliest time when we have to do rebalance again */
|
|
unsigned long next_balance = jiffies + 60*HZ;
|
|
int update_next_balance = 0;
|
|
int need_serialize, need_decay = 0;
|
|
u64 max_cost = 0;
|
|
|
|
update_blocked_averages(cpu);
|
|
|
|
rcu_read_lock();
|
|
for_each_domain(cpu, sd) {
|
|
/*
|
|
* Decay the newidle max times here because this is a regular
|
|
* visit to all the domains. Decay ~1% per second.
|
|
*/
|
|
if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
|
|
sd->max_newidle_lb_cost =
|
|
(sd->max_newidle_lb_cost * 253) / 256;
|
|
sd->next_decay_max_lb_cost = jiffies + HZ;
|
|
need_decay = 1;
|
|
}
|
|
max_cost += sd->max_newidle_lb_cost;
|
|
|
|
if (!(sd->flags & SD_LOAD_BALANCE))
|
|
continue;
|
|
|
|
/*
|
|
* Stop the load balance at this level. There is another
|
|
* CPU in our sched group which is doing load balancing more
|
|
* actively.
|
|
*/
|
|
if (!continue_balancing) {
|
|
if (need_decay)
|
|
continue;
|
|
break;
|
|
}
|
|
|
|
interval = sd->balance_interval;
|
|
if (idle != CPU_IDLE)
|
|
interval *= sd->busy_factor;
|
|
|
|
/* scale ms to jiffies */
|
|
interval = msecs_to_jiffies(interval);
|
|
interval = clamp(interval, 1UL, max_load_balance_interval);
|
|
|
|
need_serialize = sd->flags & SD_SERIALIZE;
|
|
|
|
if (need_serialize) {
|
|
if (!spin_trylock(&balancing))
|
|
goto out;
|
|
}
|
|
|
|
if (time_after_eq(jiffies, sd->last_balance + interval)) {
|
|
if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
|
|
/*
|
|
* The LBF_DST_PINNED logic could have changed
|
|
* env->dst_cpu, so we can't know our idle
|
|
* state even if we migrated tasks. Update it.
|
|
*/
|
|
idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
|
|
}
|
|
sd->last_balance = jiffies;
|
|
}
|
|
if (need_serialize)
|
|
spin_unlock(&balancing);
|
|
out:
|
|
if (time_after(next_balance, sd->last_balance + interval)) {
|
|
next_balance = sd->last_balance + interval;
|
|
update_next_balance = 1;
|
|
}
|
|
}
|
|
if (need_decay) {
|
|
/*
|
|
* Ensure the rq-wide value also decays but keep it at a
|
|
* reasonable floor to avoid funnies with rq->avg_idle.
|
|
*/
|
|
rq->max_idle_balance_cost =
|
|
max((u64)sysctl_sched_migration_cost, max_cost);
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* next_balance will be updated only when there is a need.
|
|
* When the cpu is attached to null domain for ex, it will not be
|
|
* updated.
|
|
*/
|
|
if (likely(update_next_balance))
|
|
rq->next_balance = next_balance;
|
|
}
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
/*
|
|
* In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
|
|
* rebalancing for all the cpus for whom scheduler ticks are stopped.
|
|
*/
|
|
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
|
|
{
|
|
struct rq *this_rq = cpu_rq(this_cpu);
|
|
struct rq *rq;
|
|
int balance_cpu;
|
|
|
|
if (idle != CPU_IDLE ||
|
|
!test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
|
|
goto end;
|
|
|
|
for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
|
|
if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
|
|
continue;
|
|
|
|
/*
|
|
* If this cpu gets work to do, stop the load balancing
|
|
* work being done for other cpus. Next load
|
|
* balancing owner will pick it up.
|
|
*/
|
|
if (need_resched())
|
|
break;
|
|
|
|
rq = cpu_rq(balance_cpu);
|
|
|
|
raw_spin_lock_irq(&rq->lock);
|
|
update_rq_clock(rq);
|
|
update_idle_cpu_load(rq);
|
|
raw_spin_unlock_irq(&rq->lock);
|
|
|
|
rebalance_domains(balance_cpu, CPU_IDLE);
|
|
|
|
if (time_after(this_rq->next_balance, rq->next_balance))
|
|
this_rq->next_balance = rq->next_balance;
|
|
}
|
|
nohz.next_balance = this_rq->next_balance;
|
|
end:
|
|
clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
|
|
}
|
|
|
|
/*
|
|
* Current heuristic for kicking the idle load balancer in the presence
|
|
* of an idle cpu is the system.
|
|
* - This rq has more than one task.
|
|
* - At any scheduler domain level, this cpu's scheduler group has multiple
|
|
* busy cpu's exceeding the group's power.
|
|
* - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
|
|
* domain span are idle.
|
|
*/
|
|
static inline int nohz_kick_needed(struct rq *rq, int cpu)
|
|
{
|
|
unsigned long now = jiffies;
|
|
struct sched_domain *sd;
|
|
struct sched_group_power *sgp;
|
|
int nr_busy;
|
|
|
|
if (unlikely(idle_cpu(cpu)))
|
|
return 0;
|
|
|
|
/*
|
|
* We may be recently in ticked or tickless idle mode. At the first
|
|
* busy tick after returning from idle, we will update the busy stats.
|
|
*/
|
|
set_cpu_sd_state_busy();
|
|
nohz_balance_exit_idle(cpu);
|
|
|
|
/*
|
|
* None are in tickless mode and hence no need for NOHZ idle load
|
|
* balancing.
|
|
*/
|
|
if (likely(!atomic_read(&nohz.nr_cpus)))
|
|
return 0;
|
|
|
|
if (time_before(now, nohz.next_balance))
|
|
return 0;
|
|
|
|
if (rq->nr_running >= 2)
|
|
goto need_kick;
|
|
|
|
rcu_read_lock();
|
|
sd = rcu_dereference(per_cpu(sd_busy, cpu));
|
|
|
|
if (sd) {
|
|
sgp = sd->groups->sgp;
|
|
nr_busy = atomic_read(&sgp->nr_busy_cpus);
|
|
|
|
if (nr_busy > 1)
|
|
goto need_kick_unlock;
|
|
}
|
|
|
|
sd = rcu_dereference(per_cpu(sd_asym, cpu));
|
|
|
|
if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
|
|
sched_domain_span(sd)) < cpu))
|
|
goto need_kick_unlock;
|
|
|
|
rcu_read_unlock();
|
|
return 0;
|
|
|
|
need_kick_unlock:
|
|
rcu_read_unlock();
|
|
need_kick:
|
|
return 1;
|
|
}
|
|
#else
|
|
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { }
|
|
#endif
|
|
|
|
/*
|
|
* run_rebalance_domains is triggered when needed from the scheduler tick.
|
|
* Also triggered for nohz idle balancing (with nohz_balancing_kick set).
|
|
*/
|
|
static void run_rebalance_domains(struct softirq_action *h)
|
|
{
|
|
int this_cpu = smp_processor_id();
|
|
struct rq *this_rq = cpu_rq(this_cpu);
|
|
enum cpu_idle_type idle = this_rq->idle_balance ?
|
|
CPU_IDLE : CPU_NOT_IDLE;
|
|
|
|
rebalance_domains(this_cpu, idle);
|
|
|
|
/*
|
|
* If this cpu has a pending nohz_balance_kick, then do the
|
|
* balancing on behalf of the other idle cpus whose ticks are
|
|
* stopped.
|
|
*/
|
|
nohz_idle_balance(this_cpu, idle);
|
|
}
|
|
|
|
static inline int on_null_domain(int cpu)
|
|
{
|
|
return !rcu_dereference_sched(cpu_rq(cpu)->sd);
|
|
}
|
|
|
|
/*
|
|
* Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
|
|
*/
|
|
void trigger_load_balance(struct rq *rq, int cpu)
|
|
{
|
|
/* Don't need to rebalance while attached to NULL domain */
|
|
if (time_after_eq(jiffies, rq->next_balance) &&
|
|
likely(!on_null_domain(cpu)))
|
|
raise_softirq(SCHED_SOFTIRQ);
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
|
|
nohz_balancer_kick(cpu);
|
|
#endif
|
|
}
|
|
|
|
static void rq_online_fair(struct rq *rq)
|
|
{
|
|
update_sysctl();
|
|
}
|
|
|
|
static void rq_offline_fair(struct rq *rq)
|
|
{
|
|
update_sysctl();
|
|
|
|
/* Ensure any throttled groups are reachable by pick_next_task */
|
|
unthrottle_offline_cfs_rqs(rq);
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* scheduler tick hitting a task of our scheduling class:
|
|
*/
|
|
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &curr->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
entity_tick(cfs_rq, se, queued);
|
|
}
|
|
|
|
if (numabalancing_enabled)
|
|
task_tick_numa(rq, curr);
|
|
|
|
update_rq_runnable_avg(rq, 1);
|
|
}
|
|
|
|
/*
|
|
* called on fork with the child task as argument from the parent's context
|
|
* - child not yet on the tasklist
|
|
* - preemption disabled
|
|
*/
|
|
static void task_fork_fair(struct task_struct *p)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se, *curr;
|
|
int this_cpu = smp_processor_id();
|
|
struct rq *rq = this_rq();
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&rq->lock, flags);
|
|
|
|
update_rq_clock(rq);
|
|
|
|
cfs_rq = task_cfs_rq(current);
|
|
curr = cfs_rq->curr;
|
|
|
|
/*
|
|
* Not only the cpu but also the task_group of the parent might have
|
|
* been changed after parent->se.parent,cfs_rq were copied to
|
|
* child->se.parent,cfs_rq. So call __set_task_cpu() to make those
|
|
* of child point to valid ones.
|
|
*/
|
|
rcu_read_lock();
|
|
__set_task_cpu(p, this_cpu);
|
|
rcu_read_unlock();
|
|
|
|
update_curr(cfs_rq);
|
|
|
|
if (curr)
|
|
se->vruntime = curr->vruntime;
|
|
place_entity(cfs_rq, se, 1);
|
|
|
|
if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
|
|
/*
|
|
* Upon rescheduling, sched_class::put_prev_task() will place
|
|
* 'current' within the tree based on its new key value.
|
|
*/
|
|
swap(curr->vruntime, se->vruntime);
|
|
resched_task(rq->curr);
|
|
}
|
|
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
|
|
raw_spin_unlock_irqrestore(&rq->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Priority of the task has changed. Check to see if we preempt
|
|
* the current task.
|
|
*/
|
|
static void
|
|
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
|
|
{
|
|
if (!p->se.on_rq)
|
|
return;
|
|
|
|
/*
|
|
* Reschedule if we are currently running on this runqueue and
|
|
* our priority decreased, or if we are not currently running on
|
|
* this runqueue and our priority is higher than the current's
|
|
*/
|
|
if (rq->curr == p) {
|
|
if (p->prio > oldprio)
|
|
resched_task(rq->curr);
|
|
} else
|
|
check_preempt_curr(rq, p, 0);
|
|
}
|
|
|
|
static void switched_from_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
/*
|
|
* Ensure the task's vruntime is normalized, so that when its
|
|
* switched back to the fair class the enqueue_entity(.flags=0) will
|
|
* do the right thing.
|
|
*
|
|
* If it was on_rq, then the dequeue_entity(.flags=0) will already
|
|
* have normalized the vruntime, if it was !on_rq, then only when
|
|
* the task is sleeping will it still have non-normalized vruntime.
|
|
*/
|
|
if (!se->on_rq && p->state != TASK_RUNNING) {
|
|
/*
|
|
* Fix up our vruntime so that the current sleep doesn't
|
|
* cause 'unlimited' sleep bonus.
|
|
*/
|
|
place_entity(cfs_rq, se, 0);
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* Remove our load from contribution when we leave sched_fair
|
|
* and ensure we don't carry in an old decay_count if we
|
|
* switch back.
|
|
*/
|
|
if (se->avg.decay_count) {
|
|
__synchronize_entity_decay(se);
|
|
subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* We switched to the sched_fair class.
|
|
*/
|
|
static void switched_to_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
if (!p->se.on_rq)
|
|
return;
|
|
|
|
/*
|
|
* We were most likely switched from sched_rt, so
|
|
* kick off the schedule if running, otherwise just see
|
|
* if we can still preempt the current task.
|
|
*/
|
|
if (rq->curr == p)
|
|
resched_task(rq->curr);
|
|
else
|
|
check_preempt_curr(rq, p, 0);
|
|
}
|
|
|
|
/* Account for a task changing its policy or group.
|
|
*
|
|
* This routine is mostly called to set cfs_rq->curr field when a task
|
|
* migrates between groups/classes.
|
|
*/
|
|
static void set_curr_task_fair(struct rq *rq)
|
|
{
|
|
struct sched_entity *se = &rq->curr->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
set_next_entity(cfs_rq, se);
|
|
/* ensure bandwidth has been allocated on our new cfs_rq */
|
|
account_cfs_rq_runtime(cfs_rq, 0);
|
|
}
|
|
}
|
|
|
|
void init_cfs_rq(struct cfs_rq *cfs_rq)
|
|
{
|
|
cfs_rq->tasks_timeline = RB_ROOT;
|
|
cfs_rq->min_vruntime = (u64)(-(1LL << 20));
|
|
#ifndef CONFIG_64BIT
|
|
cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
|
|
#endif
|
|
#ifdef CONFIG_SMP
|
|
atomic64_set(&cfs_rq->decay_counter, 1);
|
|
atomic_long_set(&cfs_rq->removed_load, 0);
|
|
#endif
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static void task_move_group_fair(struct task_struct *p, int on_rq)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
/*
|
|
* If the task was not on the rq at the time of this cgroup movement
|
|
* it must have been asleep, sleeping tasks keep their ->vruntime
|
|
* absolute on their old rq until wakeup (needed for the fair sleeper
|
|
* bonus in place_entity()).
|
|
*
|
|
* If it was on the rq, we've just 'preempted' it, which does convert
|
|
* ->vruntime to a relative base.
|
|
*
|
|
* Make sure both cases convert their relative position when migrating
|
|
* to another cgroup's rq. This does somewhat interfere with the
|
|
* fair sleeper stuff for the first placement, but who cares.
|
|
*/
|
|
/*
|
|
* When !on_rq, vruntime of the task has usually NOT been normalized.
|
|
* But there are some cases where it has already been normalized:
|
|
*
|
|
* - Moving a forked child which is waiting for being woken up by
|
|
* wake_up_new_task().
|
|
* - Moving a task which has been woken up by try_to_wake_up() and
|
|
* waiting for actually being woken up by sched_ttwu_pending().
|
|
*
|
|
* To prevent boost or penalty in the new cfs_rq caused by delta
|
|
* min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
|
|
*/
|
|
if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
|
|
on_rq = 1;
|
|
|
|
if (!on_rq)
|
|
p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
|
|
set_task_rq(p, task_cpu(p));
|
|
if (!on_rq) {
|
|
cfs_rq = cfs_rq_of(&p->se);
|
|
p->se.vruntime += cfs_rq->min_vruntime;
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* migrate_task_rq_fair() will have removed our previous
|
|
* contribution, but we must synchronize for ongoing future
|
|
* decay.
|
|
*/
|
|
p->se.avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
|
|
cfs_rq->blocked_load_avg += p->se.avg.load_avg_contrib;
|
|
#endif
|
|
}
|
|
}
|
|
|
|
void free_fair_sched_group(struct task_group *tg)
|
|
{
|
|
int i;
|
|
|
|
destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
|
|
|
|
for_each_possible_cpu(i) {
|
|
if (tg->cfs_rq)
|
|
kfree(tg->cfs_rq[i]);
|
|
if (tg->se)
|
|
kfree(tg->se[i]);
|
|
}
|
|
|
|
kfree(tg->cfs_rq);
|
|
kfree(tg->se);
|
|
}
|
|
|
|
int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se;
|
|
int i;
|
|
|
|
tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
|
|
if (!tg->cfs_rq)
|
|
goto err;
|
|
tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
|
|
if (!tg->se)
|
|
goto err;
|
|
|
|
tg->shares = NICE_0_LOAD;
|
|
|
|
init_cfs_bandwidth(tg_cfs_bandwidth(tg));
|
|
|
|
for_each_possible_cpu(i) {
|
|
cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
|
|
GFP_KERNEL, cpu_to_node(i));
|
|
if (!cfs_rq)
|
|
goto err;
|
|
|
|
se = kzalloc_node(sizeof(struct sched_entity),
|
|
GFP_KERNEL, cpu_to_node(i));
|
|
if (!se)
|
|
goto err_free_rq;
|
|
|
|
init_cfs_rq(cfs_rq);
|
|
init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
|
|
}
|
|
|
|
return 1;
|
|
|
|
err_free_rq:
|
|
kfree(cfs_rq);
|
|
err:
|
|
return 0;
|
|
}
|
|
|
|
void unregister_fair_sched_group(struct task_group *tg, int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* Only empty task groups can be destroyed; so we can speculatively
|
|
* check on_list without danger of it being re-added.
|
|
*/
|
|
if (!tg->cfs_rq[cpu]->on_list)
|
|
return;
|
|
|
|
raw_spin_lock_irqsave(&rq->lock, flags);
|
|
list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
|
|
raw_spin_unlock_irqrestore(&rq->lock, flags);
|
|
}
|
|
|
|
void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
|
|
struct sched_entity *se, int cpu,
|
|
struct sched_entity *parent)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
cfs_rq->tg = tg;
|
|
cfs_rq->rq = rq;
|
|
init_cfs_rq_runtime(cfs_rq);
|
|
|
|
tg->cfs_rq[cpu] = cfs_rq;
|
|
tg->se[cpu] = se;
|
|
|
|
/* se could be NULL for root_task_group */
|
|
if (!se)
|
|
return;
|
|
|
|
if (!parent)
|
|
se->cfs_rq = &rq->cfs;
|
|
else
|
|
se->cfs_rq = parent->my_q;
|
|
|
|
se->my_q = cfs_rq;
|
|
/* guarantee group entities always have weight */
|
|
update_load_set(&se->load, NICE_0_LOAD);
|
|
se->parent = parent;
|
|
}
|
|
|
|
static DEFINE_MUTEX(shares_mutex);
|
|
|
|
int sched_group_set_shares(struct task_group *tg, unsigned long shares)
|
|
{
|
|
int i;
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* We can't change the weight of the root cgroup.
|
|
*/
|
|
if (!tg->se[0])
|
|
return -EINVAL;
|
|
|
|
shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
|
|
|
|
mutex_lock(&shares_mutex);
|
|
if (tg->shares == shares)
|
|
goto done;
|
|
|
|
tg->shares = shares;
|
|
for_each_possible_cpu(i) {
|
|
struct rq *rq = cpu_rq(i);
|
|
struct sched_entity *se;
|
|
|
|
se = tg->se[i];
|
|
/* Propagate contribution to hierarchy */
|
|
raw_spin_lock_irqsave(&rq->lock, flags);
|
|
|
|
/* Possible calls to update_curr() need rq clock */
|
|
update_rq_clock(rq);
|
|
for_each_sched_entity(se)
|
|
update_cfs_shares(group_cfs_rq(se));
|
|
raw_spin_unlock_irqrestore(&rq->lock, flags);
|
|
}
|
|
|
|
done:
|
|
mutex_unlock(&shares_mutex);
|
|
return 0;
|
|
}
|
|
#else /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
void free_fair_sched_group(struct task_group *tg) { }
|
|
|
|
int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
|
|
{
|
|
return 1;
|
|
}
|
|
|
|
void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
|
|
|
|
#endif /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
|
|
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
|
|
{
|
|
struct sched_entity *se = &task->se;
|
|
unsigned int rr_interval = 0;
|
|
|
|
/*
|
|
* Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
|
|
* idle runqueue:
|
|
*/
|
|
if (rq->cfs.load.weight)
|
|
rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
|
|
|
|
return rr_interval;
|
|
}
|
|
|
|
/*
|
|
* All the scheduling class methods:
|
|
*/
|
|
const struct sched_class fair_sched_class = {
|
|
.next = &idle_sched_class,
|
|
.enqueue_task = enqueue_task_fair,
|
|
.dequeue_task = dequeue_task_fair,
|
|
.yield_task = yield_task_fair,
|
|
.yield_to_task = yield_to_task_fair,
|
|
|
|
.check_preempt_curr = check_preempt_wakeup,
|
|
|
|
.pick_next_task = pick_next_task_fair,
|
|
.put_prev_task = put_prev_task_fair,
|
|
|
|
#ifdef CONFIG_SMP
|
|
.select_task_rq = select_task_rq_fair,
|
|
.migrate_task_rq = migrate_task_rq_fair,
|
|
|
|
.rq_online = rq_online_fair,
|
|
.rq_offline = rq_offline_fair,
|
|
|
|
.task_waking = task_waking_fair,
|
|
#endif
|
|
|
|
.set_curr_task = set_curr_task_fair,
|
|
.task_tick = task_tick_fair,
|
|
.task_fork = task_fork_fair,
|
|
|
|
.prio_changed = prio_changed_fair,
|
|
.switched_from = switched_from_fair,
|
|
.switched_to = switched_to_fair,
|
|
|
|
.get_rr_interval = get_rr_interval_fair,
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
.task_move_group = task_move_group_fair,
|
|
#endif
|
|
};
|
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
void print_cfs_stats(struct seq_file *m, int cpu)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
rcu_read_lock();
|
|
for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
|
|
print_cfs_rq(m, cpu, cfs_rq);
|
|
rcu_read_unlock();
|
|
}
|
|
#endif
|
|
|
|
__init void init_sched_fair_class(void)
|
|
{
|
|
#ifdef CONFIG_SMP
|
|
open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
nohz.next_balance = jiffies;
|
|
zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
|
|
cpu_notifier(sched_ilb_notifier, 0);
|
|
#endif
|
|
#endif /* SMP */
|
|
|
|
}
|