mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-11 23:26:47 +07:00
20ae00792c
Percpu allocator now supports allocation mask. Add @gfp to [flex_]proportions init functions so that !GFP_KERNEL allocation masks can be used with them too. This patch doesn't make any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Peter Zijlstra <peterz@infradead.org>
408 lines
9.4 KiB
C
408 lines
9.4 KiB
C
/*
|
|
* Floating proportions
|
|
*
|
|
* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
|
|
*
|
|
* Description:
|
|
*
|
|
* The floating proportion is a time derivative with an exponentially decaying
|
|
* history:
|
|
*
|
|
* p_{j} = \Sum_{i=0} (dx_{j}/dt_{-i}) / 2^(1+i)
|
|
*
|
|
* Where j is an element from {prop_local}, x_{j} is j's number of events,
|
|
* and i the time period over which the differential is taken. So d/dt_{-i} is
|
|
* the differential over the i-th last period.
|
|
*
|
|
* The decaying history gives smooth transitions. The time differential carries
|
|
* the notion of speed.
|
|
*
|
|
* The denominator is 2^(1+i) because we want the series to be normalised, ie.
|
|
*
|
|
* \Sum_{i=0} 1/2^(1+i) = 1
|
|
*
|
|
* Further more, if we measure time (t) in the same events as x; so that:
|
|
*
|
|
* t = \Sum_{j} x_{j}
|
|
*
|
|
* we get that:
|
|
*
|
|
* \Sum_{j} p_{j} = 1
|
|
*
|
|
* Writing this in an iterative fashion we get (dropping the 'd's):
|
|
*
|
|
* if (++x_{j}, ++t > period)
|
|
* t /= 2;
|
|
* for_each (j)
|
|
* x_{j} /= 2;
|
|
*
|
|
* so that:
|
|
*
|
|
* p_{j} = x_{j} / t;
|
|
*
|
|
* We optimize away the '/= 2' for the global time delta by noting that:
|
|
*
|
|
* if (++t > period) t /= 2:
|
|
*
|
|
* Can be approximated by:
|
|
*
|
|
* period/2 + (++t % period/2)
|
|
*
|
|
* [ Furthermore, when we choose period to be 2^n it can be written in terms of
|
|
* binary operations and wraparound artefacts disappear. ]
|
|
*
|
|
* Also note that this yields a natural counter of the elapsed periods:
|
|
*
|
|
* c = t / (period/2)
|
|
*
|
|
* [ Its monotonic increasing property can be applied to mitigate the wrap-
|
|
* around issue. ]
|
|
*
|
|
* This allows us to do away with the loop over all prop_locals on each period
|
|
* expiration. By remembering the period count under which it was last accessed
|
|
* as c_{j}, we can obtain the number of 'missed' cycles from:
|
|
*
|
|
* c - c_{j}
|
|
*
|
|
* We can then lazily catch up to the global period count every time we are
|
|
* going to use x_{j}, by doing:
|
|
*
|
|
* x_{j} /= 2^(c - c_{j}), c_{j} = c
|
|
*/
|
|
|
|
#include <linux/proportions.h>
|
|
#include <linux/rcupdate.h>
|
|
|
|
int prop_descriptor_init(struct prop_descriptor *pd, int shift, gfp_t gfp)
|
|
{
|
|
int err;
|
|
|
|
if (shift > PROP_MAX_SHIFT)
|
|
shift = PROP_MAX_SHIFT;
|
|
|
|
pd->index = 0;
|
|
pd->pg[0].shift = shift;
|
|
mutex_init(&pd->mutex);
|
|
err = percpu_counter_init(&pd->pg[0].events, 0, gfp);
|
|
if (err)
|
|
goto out;
|
|
|
|
err = percpu_counter_init(&pd->pg[1].events, 0, gfp);
|
|
if (err)
|
|
percpu_counter_destroy(&pd->pg[0].events);
|
|
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* We have two copies, and flip between them to make it seem like an atomic
|
|
* update. The update is not really atomic wrt the events counter, but
|
|
* it is internally consistent with the bit layout depending on shift.
|
|
*
|
|
* We copy the events count, move the bits around and flip the index.
|
|
*/
|
|
void prop_change_shift(struct prop_descriptor *pd, int shift)
|
|
{
|
|
int index;
|
|
int offset;
|
|
u64 events;
|
|
unsigned long flags;
|
|
|
|
if (shift > PROP_MAX_SHIFT)
|
|
shift = PROP_MAX_SHIFT;
|
|
|
|
mutex_lock(&pd->mutex);
|
|
|
|
index = pd->index ^ 1;
|
|
offset = pd->pg[pd->index].shift - shift;
|
|
if (!offset)
|
|
goto out;
|
|
|
|
pd->pg[index].shift = shift;
|
|
|
|
local_irq_save(flags);
|
|
events = percpu_counter_sum(&pd->pg[pd->index].events);
|
|
if (offset < 0)
|
|
events <<= -offset;
|
|
else
|
|
events >>= offset;
|
|
percpu_counter_set(&pd->pg[index].events, events);
|
|
|
|
/*
|
|
* ensure the new pg is fully written before the switch
|
|
*/
|
|
smp_wmb();
|
|
pd->index = index;
|
|
local_irq_restore(flags);
|
|
|
|
synchronize_rcu();
|
|
|
|
out:
|
|
mutex_unlock(&pd->mutex);
|
|
}
|
|
|
|
/*
|
|
* wrap the access to the data in an rcu_read_lock() section;
|
|
* this is used to track the active references.
|
|
*/
|
|
static struct prop_global *prop_get_global(struct prop_descriptor *pd)
|
|
__acquires(RCU)
|
|
{
|
|
int index;
|
|
|
|
rcu_read_lock();
|
|
index = pd->index;
|
|
/*
|
|
* match the wmb from vcd_flip()
|
|
*/
|
|
smp_rmb();
|
|
return &pd->pg[index];
|
|
}
|
|
|
|
static void prop_put_global(struct prop_descriptor *pd, struct prop_global *pg)
|
|
__releases(RCU)
|
|
{
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
static void
|
|
prop_adjust_shift(int *pl_shift, unsigned long *pl_period, int new_shift)
|
|
{
|
|
int offset = *pl_shift - new_shift;
|
|
|
|
if (!offset)
|
|
return;
|
|
|
|
if (offset < 0)
|
|
*pl_period <<= -offset;
|
|
else
|
|
*pl_period >>= offset;
|
|
|
|
*pl_shift = new_shift;
|
|
}
|
|
|
|
/*
|
|
* PERCPU
|
|
*/
|
|
|
|
#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
|
|
|
|
int prop_local_init_percpu(struct prop_local_percpu *pl, gfp_t gfp)
|
|
{
|
|
raw_spin_lock_init(&pl->lock);
|
|
pl->shift = 0;
|
|
pl->period = 0;
|
|
return percpu_counter_init(&pl->events, 0, gfp);
|
|
}
|
|
|
|
void prop_local_destroy_percpu(struct prop_local_percpu *pl)
|
|
{
|
|
percpu_counter_destroy(&pl->events);
|
|
}
|
|
|
|
/*
|
|
* Catch up with missed period expirations.
|
|
*
|
|
* until (c_{j} == c)
|
|
* x_{j} -= x_{j}/2;
|
|
* c_{j}++;
|
|
*/
|
|
static
|
|
void prop_norm_percpu(struct prop_global *pg, struct prop_local_percpu *pl)
|
|
{
|
|
unsigned long period = 1UL << (pg->shift - 1);
|
|
unsigned long period_mask = ~(period - 1);
|
|
unsigned long global_period;
|
|
unsigned long flags;
|
|
|
|
global_period = percpu_counter_read(&pg->events);
|
|
global_period &= period_mask;
|
|
|
|
/*
|
|
* Fast path - check if the local and global period count still match
|
|
* outside of the lock.
|
|
*/
|
|
if (pl->period == global_period)
|
|
return;
|
|
|
|
raw_spin_lock_irqsave(&pl->lock, flags);
|
|
prop_adjust_shift(&pl->shift, &pl->period, pg->shift);
|
|
|
|
/*
|
|
* For each missed period, we half the local counter.
|
|
* basically:
|
|
* pl->events >> (global_period - pl->period);
|
|
*/
|
|
period = (global_period - pl->period) >> (pg->shift - 1);
|
|
if (period < BITS_PER_LONG) {
|
|
s64 val = percpu_counter_read(&pl->events);
|
|
|
|
if (val < (nr_cpu_ids * PROP_BATCH))
|
|
val = percpu_counter_sum(&pl->events);
|
|
|
|
__percpu_counter_add(&pl->events, -val + (val >> period),
|
|
PROP_BATCH);
|
|
} else
|
|
percpu_counter_set(&pl->events, 0);
|
|
|
|
pl->period = global_period;
|
|
raw_spin_unlock_irqrestore(&pl->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* ++x_{j}, ++t
|
|
*/
|
|
void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
|
|
{
|
|
struct prop_global *pg = prop_get_global(pd);
|
|
|
|
prop_norm_percpu(pg, pl);
|
|
__percpu_counter_add(&pl->events, 1, PROP_BATCH);
|
|
percpu_counter_add(&pg->events, 1);
|
|
prop_put_global(pd, pg);
|
|
}
|
|
|
|
/*
|
|
* identical to __prop_inc_percpu, except that it limits this pl's fraction to
|
|
* @frac/PROP_FRAC_BASE by ignoring events when this limit has been exceeded.
|
|
*/
|
|
void __prop_inc_percpu_max(struct prop_descriptor *pd,
|
|
struct prop_local_percpu *pl, long frac)
|
|
{
|
|
struct prop_global *pg = prop_get_global(pd);
|
|
|
|
prop_norm_percpu(pg, pl);
|
|
|
|
if (unlikely(frac != PROP_FRAC_BASE)) {
|
|
unsigned long period_2 = 1UL << (pg->shift - 1);
|
|
unsigned long counter_mask = period_2 - 1;
|
|
unsigned long global_count;
|
|
long numerator, denominator;
|
|
|
|
numerator = percpu_counter_read_positive(&pl->events);
|
|
global_count = percpu_counter_read(&pg->events);
|
|
denominator = period_2 + (global_count & counter_mask);
|
|
|
|
if (numerator > ((denominator * frac) >> PROP_FRAC_SHIFT))
|
|
goto out_put;
|
|
}
|
|
|
|
percpu_counter_add(&pl->events, 1);
|
|
percpu_counter_add(&pg->events, 1);
|
|
|
|
out_put:
|
|
prop_put_global(pd, pg);
|
|
}
|
|
|
|
/*
|
|
* Obtain a fraction of this proportion
|
|
*
|
|
* p_{j} = x_{j} / (period/2 + t % period/2)
|
|
*/
|
|
void prop_fraction_percpu(struct prop_descriptor *pd,
|
|
struct prop_local_percpu *pl,
|
|
long *numerator, long *denominator)
|
|
{
|
|
struct prop_global *pg = prop_get_global(pd);
|
|
unsigned long period_2 = 1UL << (pg->shift - 1);
|
|
unsigned long counter_mask = period_2 - 1;
|
|
unsigned long global_count;
|
|
|
|
prop_norm_percpu(pg, pl);
|
|
*numerator = percpu_counter_read_positive(&pl->events);
|
|
|
|
global_count = percpu_counter_read(&pg->events);
|
|
*denominator = period_2 + (global_count & counter_mask);
|
|
|
|
prop_put_global(pd, pg);
|
|
}
|
|
|
|
/*
|
|
* SINGLE
|
|
*/
|
|
|
|
int prop_local_init_single(struct prop_local_single *pl)
|
|
{
|
|
raw_spin_lock_init(&pl->lock);
|
|
pl->shift = 0;
|
|
pl->period = 0;
|
|
pl->events = 0;
|
|
return 0;
|
|
}
|
|
|
|
void prop_local_destroy_single(struct prop_local_single *pl)
|
|
{
|
|
}
|
|
|
|
/*
|
|
* Catch up with missed period expirations.
|
|
*/
|
|
static
|
|
void prop_norm_single(struct prop_global *pg, struct prop_local_single *pl)
|
|
{
|
|
unsigned long period = 1UL << (pg->shift - 1);
|
|
unsigned long period_mask = ~(period - 1);
|
|
unsigned long global_period;
|
|
unsigned long flags;
|
|
|
|
global_period = percpu_counter_read(&pg->events);
|
|
global_period &= period_mask;
|
|
|
|
/*
|
|
* Fast path - check if the local and global period count still match
|
|
* outside of the lock.
|
|
*/
|
|
if (pl->period == global_period)
|
|
return;
|
|
|
|
raw_spin_lock_irqsave(&pl->lock, flags);
|
|
prop_adjust_shift(&pl->shift, &pl->period, pg->shift);
|
|
/*
|
|
* For each missed period, we half the local counter.
|
|
*/
|
|
period = (global_period - pl->period) >> (pg->shift - 1);
|
|
if (likely(period < BITS_PER_LONG))
|
|
pl->events >>= period;
|
|
else
|
|
pl->events = 0;
|
|
pl->period = global_period;
|
|
raw_spin_unlock_irqrestore(&pl->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* ++x_{j}, ++t
|
|
*/
|
|
void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
|
|
{
|
|
struct prop_global *pg = prop_get_global(pd);
|
|
|
|
prop_norm_single(pg, pl);
|
|
pl->events++;
|
|
percpu_counter_add(&pg->events, 1);
|
|
prop_put_global(pd, pg);
|
|
}
|
|
|
|
/*
|
|
* Obtain a fraction of this proportion
|
|
*
|
|
* p_{j} = x_{j} / (period/2 + t % period/2)
|
|
*/
|
|
void prop_fraction_single(struct prop_descriptor *pd,
|
|
struct prop_local_single *pl,
|
|
long *numerator, long *denominator)
|
|
{
|
|
struct prop_global *pg = prop_get_global(pd);
|
|
unsigned long period_2 = 1UL << (pg->shift - 1);
|
|
unsigned long counter_mask = period_2 - 1;
|
|
unsigned long global_count;
|
|
|
|
prop_norm_single(pg, pl);
|
|
*numerator = pl->events;
|
|
|
|
global_count = percpu_counter_read(&pg->events);
|
|
*denominator = period_2 + (global_count & counter_mask);
|
|
|
|
prop_put_global(pd, pg);
|
|
}
|