linux-kernel - Re: [Question] How does perf still record the stack of a specified pid even when that process is interrupted and CPU is scheduled to other process

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Message-ID: <553A49FC.9010002@gmail.com>
Date:	Fri, 24 Apr 2015 07:49:48 -0600
From:	David Ahern <dsahern@...il.com>
To:	Yunlong Song <yunlong.song@...wei.com>, a.p.zijlstra@...llo.nl,
	paulus@...ba.org, mingo@...hat.com,
	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	linux-kernel@...r.kernel.org, wangnan0@...wei.com
Subject: Re: [Question] How does perf still record the stack of a specified
 pid even when that process is interrupted and CPU is scheduled to other process

On 4/24/15 7:31 AM, Yunlong Song wrote:
> [Profiling Problem]
>
> Although perf can record the events (with call stack) of a specified pid, e.g. using
> "perf record -g iozone -s 262144 -r 64 -i 0 -i 2". But we find iozone is interrupted

That command tells perf to *only* collect data for iozone. This command:

     perf record -g -a -- iozone ....

tells perf to collect samples system wide as long as the iozone process 
is alive.

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