linux-kernel - Re: [RFC PATCH] drivers: char: Add a dynamic clock for the trace clock

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Date:	Wed, 11 Dec 2013 21:11:42 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Sonny Rao <sonnyrao@...omium.org>
Cc:	Stephane Eranian <eranian@...gle.com>,
	Josh Triplett <josh@...htriplett.org>,
	LKML <linux-kernel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>,
	Olof Johansson <olof@...om.net>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, pawel.moll@....com
Subject: Re: [RFC PATCH] drivers: char: Add a dynamic clock for the trace
 clock

On Wed, 11 Dec 2013 18:06:06 -0800
Sonny Rao <sonnyrao@...omium.org> wrote:


> > ftrace has several clocks that it uses:
> >
> > o local - basically sched_clock()
> > o global - something like hpet that is monotonic across CPUs but slower
> > o counter - a simple atomic counter (no time associated to it)
> > o uptime - jiffy counter
> > o perf  - trace_clock, which is what perf uses
> > o x86_tsc - the raw tsc counter.
> >
> > # cat /sys/kernel/debug/trace_clock
> > [local] global counter uptime perf x86-tsc
> >
> 
> Ah ok sorry for the incorrect info there, thanks for clarifying.
> So, If I wanted to make sure everything is synced up between ftrace
> events and perf events I should say perf here instead of local.

Correct, that's why I created that clock.

-- Steve
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