From: Song Liu <songliubraving@fb.com>
To: open list <linux-kernel@vger.kernel.org>
Cc: Kernel Team <Kernel-team@fb.com>,
Peter Zijlstra <peterz@infradead.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Jiri Olsa <jolsa@kernel.org>,
Alexey Budankov <alexey.budankov@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH v9] perf: Sharing PMU counters across compatible events
Date: Thu, 2 Jan 2020 18:45:57 +0000 [thread overview]
Message-ID: <856C187D-56B4-49D8-9716-79900DD80246@fb.com> (raw)
In-Reply-To: <20191217175948.3298747-1-songliubraving@fb.com>
Hi Peter,
> On Dec 17, 2019, at 9:59 AM, Song Liu <songliubraving@fb.com> wrote:
>
> This patch tries to enable PMU sharing. When multiple perf_events are
> counting the same metric, they can share the hardware PMU counter. We
> call these events as "compatible events".
>
> The PMU sharing are limited to events within the same perf_event_context
> (ctx). When a event is installed or enabled, search the ctx for compatible
> events. This is implemented in perf_event_setup_dup(). One of these
> compatible events are picked as the master (stored in event->dup_master).
> Similarly, when the event is removed or disabled, perf_event_remove_dup()
> is used to clean up sharing.
>
> A new state PERF_EVENT_STATE_ENABLED is introduced for the master event.
> This state is used when the slave event is ACTIVE, but the master event
> is not.
>
> On the critical paths (add, del read), sharing PMU counters doesn't
> increase the complexity. Helper functions event_pmu_[add|del|read]() are
> introduced to cover these cases. All these functions have O(1) time
> complexity.
>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Tejun Heo <tj@kernel.org>
> Signed-off-by: Song Liu <songliubraving@fb.com>
Happy New Year! Wish you a great 2020!
Could you please share feedbacks on this version?
Thanks,
Song
next prev parent reply other threads:[~2020-01-02 18:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-17 17:59 [PATCH v9] perf: Sharing PMU counters across compatible events Song Liu
2020-01-02 18:45 ` Song Liu [this message]
2020-01-10 12:59 ` Peter Zijlstra
2020-01-10 17:37 ` Song Liu
2020-01-16 23:59 ` Song Liu
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