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

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Message-ID: <4B288F04.5080108@cn.fujitsu.com>
Date:	Wed, 16 Dec 2009 15:40:52 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Paul Mackerras <paulus@...ba.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	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



Ingo Molnar wrote:

>>>
>> 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
> 
> We could export HZ as part of the ftrace event format file, in 
> /debug/tracing/events/timers/ or so. Not sure what the best way would be to do 
> it (without causing runtime overhead in event processing), but we should 
> reduce our reliance on /proc and export such instrumentation information via a 
> single, coherent interface.
> 

Hi ingo,

Um, if we export this value in tracepoint format, it should add for every timer's
tracepoint.

> There's a couple of other 'system settings' values that would be useful to 
> expose in such a way - for example the number of online CPUs. (in fact that 
> could be exposed as a set of online/offline events plus a way to read the 
> current count as well)
> 


How about export those values in debugfs/tracing/*? perf tracepoint self depend on
this filesystem. 

Thanks,
Xiao
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