linux-kernel - RE: [PATCH V2 1/1] perf/core: don't find side-band event from all pmus

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Date:	Thu, 12 May 2016 13:30:36 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"eranian@...gle.com" <eranian@...gle.com>,
	"vincent.weaver@...ne.edu" <vincent.weaver@...ne.edu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"acme@...hat.com" <acme@...hat.com>,
	"jolsa@...hat.com" <jolsa@...hat.com>,
	"alexander.shishkin@...ux.intel.com" 
	<alexander.shishkin@...ux.intel.com>,
	"ying.huang@...ux.intel.com" <ying.huang@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V2 1/1] perf/core: don't find side-band event from all
 pmus



> ---
> Subject: perf/core: don't find side-band event from all pmus
> From: Kan Liang <kan.liang@...el.com>
> Date: Wed, 23 Mar 2016 11:24:37 -0700
> 
Hi Peter,

Is there something wrong with the patch?
The last time I saw this patch was in your personal tree (kernel/git/peterz/queue.git).
But now I cannot find it anymore. 

Thanks,
Kan
> perf_event_aux funciton goes through all pmus and all events in whatever
> contexts to find the side-band event to output, which is unnecessary and
> expensive.
> 
> For example, the brk test case in lkp triggers many mmap operations, at the
> time, perf with cycles:pp is also running on the system. As a result, many
> perf_event_aux are invoked, and each would search all pmus and all events.
> If we enable the uncore support (even when uncore event are not really
> used), dozens of uncore pmus will be added into pmus list, which can
> significantly decrease brk_test's ops_per_sec. Based on our test, the
> ops_per_sec without uncore patch is 2647573, while the ops_per_sec with
> uncore patch is only 1768444, which is a 33.2% reduction.
> 
> To get at the per cpu side-band event, this patch put the side-band events to
> four categories, which are tracked by 4 per-cpu lists. It only finds the
> interested events from masked category.
> To get at the per task side-band event, each task context for current task will
> be searched. Because we don't want to go update more global state on
> context switch.
> 
> 
> Cc: vincent.weaver@...ne.edu
> Cc: mingo@...nel.org
> Cc: acme@...hat.com
> Cc: ak@...ux.intel.com
> Cc: jolsa@...hat.com
> Cc: tglx@...utronix.de
> Cc: eranian@...gle.com
> Cc: alexander.shishkin@...ux.intel.com
> Reported-by: Huang, Ying <ying.huang@...ux.intel.com>
> Suggested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Kan Liang <kan.liang@...el.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Link: http://lkml.kernel.org/r/1458757477-3781-1-git-send-email-
> kan.liang@...el.com