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perf: Migrate perf to use new tick dependency mask model

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Instead of providing asynchronous checks for the nohz subsystem to verify
perf event tick dependency, migrate perf to the new mask.

Perf needs the tick for two situations:

1) Freq events. We could set the tick dependency when those are
installed on a CPU context. But setting a global dependency on top of
the global freq events accounting is much easier. If people want that
to be optimized, we can still refine that on the per-CPU tick dependency
level. This patch dooesn't change the current behaviour anyway.

2) Throttled events: this is a per-cpu dependency.

Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Frederic Weisbecker 2015-07-16 17:42:29 +02:00
parent e6e6cc22e0
commit 555e0c1ef7
4 changed files with 49 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/perf_event.h
View File

@ -1108,12 +1108,6 @@ static inline void perf_event_task_tick(void) { }
static inline int perf_event_release_kernel(struct perf_event *event) { return 0; }
#endif
#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_NO_HZ_FULL)
extern bool perf_event_can_stop_tick(void);
#else
static inline bool perf_event_can_stop_tick(void) { return true; }
#endif
#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
extern void perf_restore_debug_store(void);
#else

2
include/linux/tick.h
View File

@ -233,7 +233,6 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal,
tick_nohz_dep_clear_signal(signal, bit);
}
extern void tick_nohz_full_kick(void);
extern void tick_nohz_full_kick_cpu(int cpu);
extern void tick_nohz_full_kick_all(void);
extern void __tick_nohz_task_switch(void);
@ -260,7 +259,6 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal,
enum tick_dep_bits bit) { }
static inline void tick_nohz_full_kick_cpu(int cpu) { }
static inline void tick_nohz_full_kick(void) { }
static inline void tick_nohz_full_kick_all(void) { }
static inline void __tick_nohz_task_switch(void) { }
#endif

65
kernel/events/core.c
View File

@ -3060,17 +3060,6 @@ static int perf_rotate_context(struct perf_cpu_context *cpuctx)
return rotate;
}
#ifdef CONFIG_NO_HZ_FULL
bool perf_event_can_stop_tick(void)
{
if (atomic_read(&nr_freq_events) ||
__this_cpu_read(perf_throttled_count))
return false;
else
return true;
}
#endif
void perf_event_task_tick(void)
{
struct list_head *head = this_cpu_ptr(&active_ctx_list);
@ -3081,6 +3070,7 @@ void perf_event_task_tick(void)
__this_cpu_inc(perf_throttled_seq);
throttled = __this_cpu_xchg(perf_throttled_count, 0);
tick_dep_clear_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS);
list_for_each_entry_safe(ctx, tmp, head, active_ctx_list)
perf_adjust_freq_unthr_context(ctx, throttled);
@ -3511,6 +3501,28 @@ static void unaccount_event_cpu(struct perf_event *event, int cpu)
atomic_dec(&per_cpu(perf_cgroup_events, cpu));
}
#ifdef CONFIG_NO_HZ_FULL
static DEFINE_SPINLOCK(nr_freq_lock);
#endif
static void unaccount_freq_event_nohz(void)
{
#ifdef CONFIG_NO_HZ_FULL
spin_lock(&nr_freq_lock);
if (atomic_dec_and_test(&nr_freq_events))
tick_nohz_dep_clear(TICK_DEP_BIT_PERF_EVENTS);
spin_unlock(&nr_freq_lock);
#endif
}
static void unaccount_freq_event(void)
{
if (tick_nohz_full_enabled())
unaccount_freq_event_nohz();
else
atomic_dec(&nr_freq_events);
}
static void unaccount_event(struct perf_event *event)
{
bool dec = false;
@ -3527,7 +3539,7 @@ static void unaccount_event(struct perf_event *event)
if (event->attr.task)
atomic_dec(&nr_task_events);
if (event->attr.freq)
atomic_dec(&nr_freq_events);
unaccount_freq_event();
if (event->attr.context_switch) {
dec = true;
atomic_dec(&nr_switch_events);
@ -6349,9 +6361,9 @@ static int __perf_event_overflow(struct perf_event *event,
if (unlikely(throttle
&& hwc->interrupts >= max_samples_per_tick)) {
__this_cpu_inc(perf_throttled_count);
tick_dep_set_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS);
hwc->interrupts = MAX_INTERRUPTS;
perf_log_throttle(event, 0);
tick_nohz_full_kick();
ret = 1;
}
}
@ -7741,6 +7753,27 @@ static void account_event_cpu(struct perf_event *event, int cpu)
atomic_inc(&per_cpu(perf_cgroup_events, cpu));
}
/* Freq events need the tick to stay alive (see perf_event_task_tick). */
static void account_freq_event_nohz(void)
{
#ifdef CONFIG_NO_HZ_FULL
/* Lock so we don't race with concurrent unaccount */
spin_lock(&nr_freq_lock);
if (atomic_inc_return(&nr_freq_events) == 1)
tick_nohz_dep_set(TICK_DEP_BIT_PERF_EVENTS);
spin_unlock(&nr_freq_lock);
#endif
}
static void account_freq_event(void)
{
if (tick_nohz_full_enabled())
account_freq_event_nohz();
else
atomic_inc(&nr_freq_events);
}
static void account_event(struct perf_event *event)
{
bool inc = false;
@ -7756,10 +7789,8 @@ static void account_event(struct perf_event *event)
atomic_inc(&nr_comm_events);
if (event->attr.task)
atomic_inc(&nr_task_events);
if (event->attr.freq) {
if (atomic_inc_return(&nr_freq_events) == 1)
tick_nohz_full_kick_all();
}
if (event->attr.freq)
account_freq_event();
if (event->attr.context_switch) {
atomic_inc(&nr_switch_events);
inc = true;

8
kernel/time/tick-sched.c
View File

@ -22,7 +22,6 @@
#include <linux/module.h>
#include <linux/irq_work.h>
#include <linux/posix-timers.h>
#include <linux/perf_event.h>
#include <linux/context_tracking.h>
#include <asm/irq_regs.h>
@ -215,11 +214,6 @@ static bool can_stop_full_tick(struct tick_sched *ts)
return false;
}
if (!perf_event_can_stop_tick()) {
trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS);
return false;
}
#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
/*
* sched_clock_tick() needs us?
@ -257,7 +251,7 @@ static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
* This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
* is NMI safe.
*/
void tick_nohz_full_kick(void)
static void tick_nohz_full_kick(void)
{
if (!tick_nohz_full_cpu(smp_processor_id()))
return;