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Message-ID: <527A5D20.3000308@gmail.com>
Date: Wed, 06 Nov 2013 08:15:44 -0700
From: David Ahern <dsahern@...il.com>
To: 秦承刚 <chenggang.qcg@...baba-inc.com>,
Chenggang Qin <chenggang.qin@...il.com>,
linux-kernel <linux-kernel@...r.kernel.org>
CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Mackerras <paulus@...ba.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
Arjan van de Ven <arjan@...ux.intel.com>,
Namhyung Kim <namhyung@...il.com>,
Yanmin Zhang <yanmin.zhang@...el.com>,
Wu Fengguang <fengguang.wu@...el.com>,
Mike Galbraith <efault@....de>,
Andrew Morton <akpm@...ux-foundation.org>,
秦承刚 <chenggang.qcg@...bao.com>
Subject: Re: 答复:[PATCH 2/4] perf tools: relate 'start' & 'end' to perf_session
On 11/6/13, 4:23 AM, 秦承刚 wrote:
> Hi David:
> The goal is to simplify transfering the times to function
> perf_session__process_events() and other functions in the sample
> processing path. Session is a parameter throughout the total sample
> processing path.
Right. By putting the time check in session code you are going to be
dropping samples related to task events too. e.g., a task is created
after the session is started and before the time window. Samples for the
task (FORK, MMAP, COMM) will get dropped as will events for other tasks
(e.g., EXIT). Then samples during the time window will not correlate
nicely/correctly to a task with a name and maps.
I have patches locally with this same idea -- collect data for a broad
time window but only show/analyze samples for a specific time window.
Instead of having the time check in the session code I have it in the
commands (report, script, etc). e.g., in sample event processing:
if (perf_time__skip_sample(sample))
goto out;
where that function has the logic to compare sample timestamps to a user
given window.
I seem to recall Namhyung send out a patch on time intervals as well.
David
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