linux-kernel - Re: [PATCH 2/2] tracing: add average time in function to function profiler

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Message-ID: <20090326222924.GA28755@elte.hu>
Date:	Thu, 26 Mar 2009 23:29:24 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Stephen Rothwell <sfr@...b.auug.org.au>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 2/2] tracing: add average time in function to function
	profiler

* Stephen Rothwell <sfr@...b.auug.org.au> wrote:

> Hi Steve,
> 
> On Wed, 25 Mar 2009 21:07:39 -0400 Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> > From: Steven Rostedt <srostedt@...hat.com>
> > 
> > Show the average time in the function (Time / Hit)
> 
> Just wondering why we need to do this in the kernel ... there is 
> already enough information for a user to figure these averages 
> out.

Well, this argument can be applied to a lot of information exposed 
in /proc and /sys. For example in theory there's no need for 
/proc/interrupts at all, because the IRQ mappings are present in the 
syslog and in /sys enumerations and the IRQ counts are present in 
/proc/stat already.

I still find /proc/interrupts very handy, despite purist arguments 
that it is redundant and that it thus should not be there.

So we provide such things when it's easy to do, when it's a 
meaningful piece of information and it is convenient to users and 
developers.

Note that the function profiler is a double-non-default item in 
/debug (you need to enable two non-default options in the .config to 
get it), so you cannot stumble on it accidentally.

	Ingo
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