Subject: Re: [PATCH v3 3/4] ftrace: add tracepoint for hrtimer
From: Peter Zijlstra <peterz@infradead.org>
To: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       Steven Rostedt <rostedt@goodmis.org>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Zhaolei <zhaolei@cn.fujitsu.com>, kosaki.motohiro@jp.fujitsu.com,
       Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       Anton Blanchard <anton@samba.org>, LKML <linux-kernel@vger.kernel.org>
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Date: Thu, 23 Jul 2009 12:07:41 +0200
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On Thu, 2009-07-23 at 18:01 +0800, Xiao Guangrong wrote:
> 
> Peter Zijlstra wrote:
> 
> > OK, so what you want to measure is the time of the actual callback
> > happening (hrtimer_entry) vs that where you would have expected it to
> > happen (hrtimer_start + delay), right?
> > 
> 
> Yes
> 
> > So what's wrong with printing the expected expiration time in the
> > hrtimer_start tracepoint in the cheap clock units?
> > 
> 
> Is "cheap clock units" means jiffies time?

Nah, something like cpu_clock() which is monotonic per-cpu and should
have high resolution where available.
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