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| author |   leilei.lin <leilei.lin@alibaba-inc.com> | 2017-08-09 08:29:21 +0800 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2017-08-10 12:08:40 +0200 |
| commit | fdccc3fb7a42ea4e4cd77d2fb8fa3a45c66ec0bf (patch) | |
| tree | 0bc643ab390edab5ded23a9fd381f058425a8438 /kernel/events/core.c | |
| parent | perf/x86/amd/uncore: Get correct number of cores sharing last level cache (diff) | |
| download | linux-dev-fdccc3fb7a42ea4e4cd77d2fb8fa3a45c66ec0bf.tar.xz linux-dev-fdccc3fb7a42ea4e4cd77d2fb8fa3a45c66ec0bf.zip | |
perf/core: Reduce context switch overhead
Skip most of the PMU context switching overhead when ctx->nr_events is 0.
50% performance overhead was observed under an extreme testcase.
Signed-off-by: leilei.lin <leilei.lin@alibaba-inc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@kernel.org
Cc: alexander.shishkin@linux.intel.com
Cc: eranian@gmail.com
Cc: jolsa@redhat.com
Cc: linxiulei@gmail.com
Cc: yang_oliver@hotmail.com
Link: http://lkml.kernel.org/r/20170809002921.69813-1-leilei.lin@alibaba-inc.com
[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events/core.c')
| -rw-r--r-- | kernel/events/core.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index ee20d4c546b5..d704e23914bf 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3211,6 +3211,13 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx, return; perf_ctx_lock(cpuctx, ctx); + /* + * We must check ctx->nr_events while holding ctx->lock, such + * that we serialize against perf_install_in_context(). + */ + if (!ctx->nr_events) + goto unlock; + perf_pmu_disable(ctx->pmu); /* * We want to keep the following priority order: @@ -3224,6 +3231,8 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx, cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE); perf_event_sched_in(cpuctx, ctx, task); perf_pmu_enable(ctx->pmu); + +unlock: perf_ctx_unlock(cpuctx, ctx); } |