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Date: Thu, 23 Jul 2015 18:42:11 +0200
From: Frederic Weisbecker <fweisbec@...il.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
Christoph Lameter <cl@...ux.com>,
Ingo Molnar <mingo@...nel.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Rik van Riel <riel@...hat.com>
Subject: [PATCH 06/10] perf: Migrate perf to use new tick dependency mask model
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 <cl@...ux.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
include/linux/perf_event.h | 6 ------
kernel/events/core.c | 19 +++++--------------
kernel/time/tick-sched.c | 6 ------
3 files changed, 5 insertions(+), 26 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2027809..ff25348 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1013,12 +1013,6 @@ static inline int __perf_event_disable(void *info) { return -1; }
static inline void perf_event_task_tick(void) { }
#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 d3dae34..9980bd9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3064,17 +3064,6 @@ 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);
@@ -3085,6 +3074,7 @@ void perf_event_task_tick(void)
__this_cpu_inc(perf_throttled_seq);
throttled = __this_cpu_xchg(perf_throttled_count, 0);
+ tick_nohz_clear_tick_dependency_this_cpu(TICK_PERF_EVENTS_BIT);
list_for_each_entry_safe(ctx, tmp, head, active_ctx_list)
perf_adjust_freq_unthr_context(ctx, throttled);
@@ -3453,7 +3443,8 @@ 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);
+ if (atomic_dec_and_test(&nr_freq_events))
+ tick_nohz_clear_tick_dependency(TICK_PERF_EVENTS_BIT);
if (is_cgroup_event(event))
static_key_slow_dec_deferred(&perf_sched_events);
if (has_branch_stack(event))
@@ -6089,9 +6080,9 @@ 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_tick_dependency_this_cpu(TICK_PERF_EVENTS_BIT);
hwc->interrupts = MAX_INTERRUPTS;
perf_log_throttle(event, 0);
- tick_nohz_full_kick();
ret = 1;
}
}
@@ -7477,7 +7468,7 @@ 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_tick_dependency(TICK_PERF_EVENTS_BIT);
}
if (has_branch_stack(event))
static_key_slow_inc(&perf_sched_events.key);
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index a64646e..fbe4736 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>
@@ -203,11 +202,6 @@ 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?
--
2.1.4
--
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