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Message-ID: <4B283596.2010801@cn.fujitsu.com>
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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