linux-kernel - Re: [PATCH v7] perf: Sharing PMU counters across compatible events

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Message-ID: <20191122193343.GB2157@krava>
Date:   Fri, 22 Nov 2019 20:33:43 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Song Liu <songliubraving@...com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, davidca@...com,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v7] perf: Sharing PMU counters across compatible events

On Fri, Nov 15, 2019 at 03:55:04PM -0800, Song Liu 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@...radead.org>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Alexey Budankov <alexey.budankov@...ux.intel.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Tejun Heo <tj@...nel.org>
> Signed-off-by: Song Liu <songliubraving@...com>
> 
> ---
> Changes in v7:
> Major rewrite to avoid allocating extra master event.

hi,
what is this based on? I can't apply it on tip/master:

	Applying: perf: Sharing PMU counters across compatible events
	error: patch failed: include/linux/perf_event.h:722
	error: include/linux/perf_event.h: patch does not apply
	Patch failed at 0001 perf: Sharing PMU counters across compatible events
	hint: Use 'git am --show-current-patch' to see the failed patch
	When you have resolved this problem, run "git am --continue".
	If you prefer to skip this patch, run "git am --skip" instead.
	To restore the original branch and stop patching, run "git am --abort".

also I'm getting this when trying to see/apply plain text patch:

	[jolsa@...l-r440-01 linux-perf]$ git am --show-current-patch | tail
	 =09=09for_each_sibling_event(sibling, group_leader) {
	 =09=09=09perf_remove_from_context(sibling, 0);
	 =09=09=09put_ctx(gctx);
	+=09=09=09WARN_ON_ONCE(sibling->dup_master);
	 =09=09}
	=20
	 =09=09/*
	--=20
	2.17.1


jirka