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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Date:	Fri, 24 Apr 2015 21:56:06 +0800
From:	Yunlong Song <yunlong.song@...wei.com>
To:	David Ahern <dsahern@...il.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 2015/4/24 21:49, David Ahern wrote:
> 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.
> 
> 
> 

But we only want the records of iozone rather than the overall system, since other process
will interfere the targeted I/O stack of the specific 1% case, and we cannot figure out the
"clean" specific stack which takes up 60% time.

-- 
Thanks,
Yunlong Song

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