From: Peter Zijlstra <peterz@infradead.org>
To: 石祤 <linxiulei@gmail.com>
Cc: yang_oliver@hotmail.com, mingo@redhat.com, acme@kernel.org,
alexander.shishkin@linux.intel.com, linux-kernel@vger.kernel.org,
tglx@linutronix.de, eranian@gmail.com,
torvalds@linux-foundation.org, jolsa@redhat.com,
"leilei.lin" <leilei.lin@alibaba-inc.com>
Subject: Re: [PATCH v3] perf/core: Avoid context switch overheads
Date: Wed, 9 Aug 2017 18:37:22 +0200 [thread overview]
Message-ID: <20170809163722.7555bmpxukvejdkp@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170809002921.69813-1-leilei.lin@alibaba-inc.com>
On Wed, Aug 09, 2017 at 08:29:21AM +0800, 石祤 wrote:
> From: "leilei.lin" <leilei.lin@alibaba-inc.com>
>
> A performance issue caused by less strickly check in task
> sched when these tasks were once attached by per-task perf_event.
>
> A task will alloc task->perf_event_ctxp[ctxn] when it was called
> by perf_event_open, and task->perf_event_ctxp[ctxn] would not
> ever be freed to NULL.
>
> __perf_event_task_sched_in()
> if (task->perf_event_ctxp[ctxn]) // here is always true
> perf_event_context_sched_in() // operate pmu
>
> 50% at most performance overhead was observed under some extreme
> test case. Therefore, add a more strick check as to ctx->nr_events,
> when ctx->nr_events == 0, it's no need to continue.
>
> Signed-off-by: leilei.lin <leilei.lin@alibaba-inc.com>
Thanks!
next prev parent reply other threads:[~2017-08-09 16:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-09 0:29 石祤
2017-08-09 16:37 ` Peter Zijlstra [this message]
2017-08-10 12:03 ` [tip:perf/core] perf/core: Reduce context switch overhead tip-bot for leilei.lin
2017-08-09 0:40 [PATCH v3] perf/core: Avoid context switch overheads linxiulei
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