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From: Stephane Eranian <eranian@google.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Jiri Olsa <jolsa@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	David Ahern <dsahern@gmail.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Milian Wolff <milian.wolff@kdab.com>,
	frederic@kernel.org
Subject: Re: [PATCH 09/10] perf/cputime: Don't stop idle tick if there's live cputime event
Date: Thu, 7 Jun 2018 09:01:30 -0700	[thread overview]
Message-ID: <CABPqkBR88VBZB1mLttUx0UxnFgWTJ=ggb66PsMti--svJU70UQ@mail.gmail.com> (raw)
In-Reply-To: <20180607154522.hyjmxn3q6zgcvsnx@two.firstfloor.org>

Hi Jiri,

On Thu, Jun 7, 2018 at 8:45 AM Andi Kleen <andi@firstfloor.org> wrote:
>
> On Thu, Jun 07, 2018 at 12:15:12AM +0200, Jiri Olsa wrote:
> > Disable stopping of the idle tick when having live cputime
> > event. When the tick is disabled, the idle counts are out
> > of date until next tick/update and perf cputime PMU provides
> > misleading counts.
>
> I really don't like this. This can totally change performance
> (e.g. less Turbo due to less idle) and performance tools shouldn't
> change the performance profile drastically.
>
You do not want to change the behavior of the kernel just because you
are monitoring.
This may introduce side effects on other events which may not otherwise exist.

  reply	other threads:[~2018-06-07 16:01 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-06 22:15 [RFC 00/10] perf: Add cputime events/metrics Jiri Olsa
2018-06-06 22:15 ` [PATCH 01/10] perf tools: Uniquify the event name if there's no other matched event Jiri Olsa
2018-06-06 23:19   ` Andi Kleen
2018-06-07  6:22     ` Jiri Olsa
2018-06-07 16:09       ` Stephane Eranian
2018-06-08  0:06         ` Jiri Olsa
2018-06-06 22:15 ` [PATCH 02/10] perf tools: Fix error index for pmu event parser Jiri Olsa
2018-06-07 18:53   ` Arnaldo Carvalho de Melo
2018-06-14  6:21   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2018-06-06 22:15 ` [PATCH 03/10] perf stat: Add --interval-clear option Jiri Olsa
2018-06-07 18:57   ` Arnaldo Carvalho de Melo
2018-06-14  6:21   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2018-06-06 22:15 ` [PATCH 04/10] perf stat: Use only color_fprintf call in print_metric_only Jiri Olsa
2018-06-07 19:00   ` Arnaldo Carvalho de Melo
2018-06-14  6:22   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2018-06-06 22:15 ` [PATCH 05/10] perf stat: Fix metric column display Jiri Olsa
2018-06-07 19:00   ` Arnaldo Carvalho de Melo
2018-06-14  6:22   ` [tip:perf/urgent] perf stat: Fix metric column header display alignment tip-bot for Jiri Olsa
2018-06-06 22:15 ` [PATCH 06/10] perf stat: Allow to specify specific metric column len Jiri Olsa
2018-06-14  6:23   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2018-06-06 22:15 ` [PATCH 07/10] perf stat: Add event parsing error handling to add_default_attributes Jiri Olsa
2018-06-07 19:04   ` Arnaldo Carvalho de Melo
2018-06-07 19:05     ` Arnaldo Carvalho de Melo
2018-06-14  6:23   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2018-06-06 22:15 ` [PATCH 08/10] perf/cputime: Add cputime pmu Jiri Olsa
2018-06-06 22:15 ` [PATCH 09/10] perf/cputime: Don't stop idle tick if there's live cputime event Jiri Olsa
2018-06-07 15:45   ` Andi Kleen
2018-06-07 16:01     ` Stephane Eranian [this message]
2018-06-08  0:12       ` Jiri Olsa
2018-06-06 22:15 ` [PATCH 10/10] perf stat: Add cputime metric support Jiri Olsa
2018-06-06 23:10 ` [RFC 00/10] perf: Add cputime events/metrics Andi Kleen
2018-09-26 14:44   ` Milian Wolff
2018-09-26 21:48     ` Jiri Olsa

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