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authorFrederic Weisbecker <fweisbec@gmail.com>2015-07-16 17:42:29 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2016-03-02 16:43:00 +0100
commit555e0c1ef7ff49ee5ac3a1eb12de4a2e4722f63d (patch)
treeede085fe6a092b648768057d988f3f11ae864d1e /kernel/events
parente6e6cc22e067a6f44449aa8fd0328404079c3ba5 (diff)
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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. 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>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c65
1 files changed, 48 insertions, 17 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5946460b2425..f23d480052e3 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3060,17 +3060,6 @@ 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);
@@ -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;