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.
Cc: Christoph Lameter <c...@linux.com>
Cc: Chris Metcalf <cmetc...@ezchip.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Luiz Capitulino <lcapitul...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Rik van Riel <r...@redhat.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Viresh Kumar <viresh.ku...@linaro.org>
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
---
include/linux/perf_event.h | 6 ------
kernel/events/core.c | 22 +++++++---------------
kernel/time/tick-sched.c | 6 ------
3 files changed, 7 insertions(+), 27 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 092a0e8..63a377f 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1023,12 +1023,6 @@ 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
diff --git a/kernel/events/core.c b/kernel/events/core.c
index b11756f..1ee70ba 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3099,17 +3099,6 @@ done:
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);
@@ -3120,6 +3109,7 @@ void perf_event_task_tick(void)
__this_cpu_inc(perf_throttled_seq);
throttled = __this_cpu_xchg(perf_throttled_count, 0);
+ tick_nohz_clear_dep_cpu(TICK_PERF_EVENTS_BIT, smp_processor_id());
list_for_each_entry_safe(ctx, tmp, head, active_ctx_list)
perf_adjust_freq_unthr_context(ctx, throttled);
@@ -3540,8 +3530,10 @@ static void unaccount_event(struct perf_event *event)
atomic_dec(&nr_comm_events);
if (event->attr.task)
atomic_dec(&nr_task_events);
- if (event->attr.freq)
- atomic_dec(&nr_freq_events);
+ if (event->attr.freq) {
+ if (atomic_dec_and_test(&nr_freq_events))
+ tick_nohz_clear_dep(TICK_PERF_EVENTS_BIT);
+ }
if (event->attr.context_switch) {
static_key_slow_dec_deferred(&perf_sched_events);
atomic_dec(&nr_switch_events);
@@ -6307,9 +6299,9 @@ 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_nohz_set_dep_cpu(TICK_PERF_EVENTS_BIT,
smp_processor_id());
hwc->interrupts = MAX_INTERRUPTS;
perf_log_throttle(event, 0);
- tick_nohz_full_kick();
ret = 1;
}
}
@@ -7695,7 +7687,7 @@ static void account_event(struct perf_event *event)
atomic_inc(&nr_task_events);
if (event->attr.freq) {
if (atomic_inc_return(&nr_freq_events) == 1)
- tick_nohz_full_kick_all();
+ tick_nohz_set_dep(TICK_PERF_EVENTS_BIT);
}
if (event->attr.context_switch) {
atomic_inc(&nr_switch_events);
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index b9ea21d..9bb19c8 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -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>
@@ -213,11 +212,6 @@ static bool can_stop_full_tick(struct tick_sched *ts)
return false;
}
- if (!perf_event_can_stop_tick()) {
- trace_tick_stop(0, "perf events running\n");
- return false;
- }
-
#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
/*
* sched_clock_tick() needs us?
--
2.5.3
--
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