linux-kernel - Re: [PATCH 0/4] perf_event: introduce 'perf timer' to analyze timer's behavior

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Date:	Wed, 16 Dec 2009 09:19:18 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] perf_event: introduce 'perf timer' to analyze	timer's
 behavior



Frederic Weisbecker wrote:
> On Tue, Dec 15, 2009 at 07:17:03PM +0800, Xiao Guangrong wrote:
>> Hi,
>>
>> We introduce 'perf timer' in this patchset, it can analyze timer
>> latency and timer function handle time, the usage and result is
>> like below:
>>
>> # perf timer record
>> # perf timer lat --print-lat --print-handle
>> -------------------------------------------------------------------------------------------------------
>> |   Timer            |   TYPE   |   Avg-latency  | Max-latency  |  Max-latency-at-TS |Max-lat-at-Task |
>> |0xf7ad1f5c          |hrtimer   |996068.500    ns|1607650     ns|10270128658526      |init            |
>> |0xf7903f04          |timer     |0.625         HZ|2           HZ|10270344082394      |swapper         |
>> |0xf787a05c          |hrtimer   |200239.500    ns|359929      ns|10269316024808      |main            |
>> |main      :[   PROF]|itimer    |0.000         HZ|0           HZ|10237021270557      |main            |
>> |main      :[VIRTUAL]|itimer    |0.000         HZ|0           HZ|10257314773501      |main            |
> 
> 
> 
> Cool! This is really a good work and a good idea.
> 
> Just have some neats in mind. hrtimers and timers don't have the same latency and
> granularity requirements.
> 
> As you show it, timers have an HZ granularity and hrtimers are about nanoseconds,
> and mixing them up in the same array of latency report is too messy.
> They don't have the same granularity/latency scope so they should
> be reported separately.
> 

Yeah, it has different unit and looks ugly :-(

but, the problem is we can't get HZ in userspace now, i'll export HZ by proc or other
way and rectify 'perf timer' output in my next work

Thanks,
Xiao
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