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Subject[PATCH 05/15] perf, core: Optimize context switch callback invoking
Date
From: "Yan, Zheng" <zheng.z.yan@intel.com>

So far only CPU pmu uses context switch callback and it is the
first registered pmu. So we can avoid iterating the whole pmu list.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
---
kernel/events/core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index fc97ed6..c281265 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2373,6 +2373,10 @@ static void perf_pmu_sched_task(struct task_struct *prev,
perf_pmu_enable(pmu);

perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
+
+ /* so far only CPU pmu uses context switch callback */
+ if (++count >= __get_cpu_var(perf_sched_cb_usages))
+ break;
}

rcu_read_unlock();
@@ -6492,7 +6496,7 @@ got_cpu_context:
if (!pmu->event_idx)
pmu->event_idx = perf_event_idx_default;

- list_add_rcu(&pmu->entry, &pmus);
+ list_add_tail_rcu(&pmu->entry, &pmus);
ret = 0;
unlock:
mutex_unlock(&pmus_lock);
--
1.8.1.4


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