linux-kernel - Re: [PATCH] tracing: branch tracer, tweak output

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Message-ID: <20081112121346.GA14739@elte.hu>
Date:	Wed, 12 Nov 2008 13:13:46 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Theodore Tso <tytso@....edu>,
	Arjan van de Ven <arjan@...radead.org>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH] tracing: branch tracer, tweak output


* Ingo Molnar <mingo@...e.hu> wrote:

> a small detail:
> 
> > For example:
> >
> >  bash-3471  [003]   357.014755: [INCORRECT] sched_info_dequeued:sched_stats.h:177
> >  bash-3471  [003]   357.014756: [correct] update_curr:sched_fair.c:489
> >  bash-3471  [003]   357.014758: [correct] calc_delta_fair:sched_fair.c:411
> >  bash-3471  [003]   357.014759: [correct] account_group_exec_runtime:sched_stats.h:356
> >  bash-3471  [003]   357.014761: [correct] update_curr:sched_fair.c:489
> >  bash-3471  [003]   357.014763: [INCORRECT] calc_delta_fair:sched_fair.c:411
> >  bash-3471  [003]   357.014765: [correct] calc_delta_mine:sched.c:1279
> 
> it's always good to have such fields aligned vertically. Something 
> like this would be shorter and visually much easier to parse:
> 
>  bash-3471  [003]   357.014755: [ MISS ] sched_info_dequeued:sched_stats.h:177
>  bash-3471  [003]   357.014756: [ .... ] update_curr:sched_fair.c:489
>  bash-3471  [003]   357.014758: [ .... ] calc_delta_fair:sched_fair.c:411
> 
> any objections against the patch below which implements this?

and note that this is really a "branch tracer/profiler", with branch 
taken/untaken prediction hits/misses. The likely()/unlikely() is an 
in-kernel tool to manually predict branch likelyhood - and for now we 
trace and profile those points that we tweaked manually - but there's 
no reason why that should be true for future versions too.

So i think it's generally better to think of these events as hit/miss 
events.

	Ingo
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