linux-kernel - Re: perf,tools: Remove usage of trace_sched

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Date:	Tue, 13 May 2014 19:14:36 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Dongsheng Yang <yangds.fnst@...fujitsu.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: perf,tools: Remove usage of trace_sched_wakeup(.success)


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Tue, May 13, 2014 at 03:34:32PM +0900, Dongsheng Yang wrote:
> > On 05/13/2014 04:22 PM, Ingo Molnar wrote:
> > >* Peter Zijlstra <peterz@...radead.org> wrote:
> > >
> > >>trace_sched_wakeup(.success) is a dead argument and has been for ages,
> > >Always 0, or random value?
> > 
> > Hi Ingo,
> > 
> > It is always 1 currently.
> > 
> > Peter believe that .success is not useful and I pointed that perf 
> > sched latency is using it now. Then he post this patch to remove 
> > the usage here.
> > 
> > Please go to the following link for more about this issue.
> 
> It is _not_ usable. You're proposing to abuse the existing 
> parameter. A wakeup doing an enqueue or not has nothing 
> _WHAT_SO_EVER_ to do with success.
> 
> Now what I think you wanted to do is make it easier to match 
> trace_sched_switch() statements with trace_sched_wakeup() 
> statements. And since you only get the trace_sched_switch() on 
> dequeue, you want to know which trace_sched_wakeup() calls did an 
> enqueue.
> 
> But that's completely and utterly unrelated to success.

So I always considered it 'the enqueue was successful' - that's I 
think why I added it to 'perf sched' originally - to be able to trace 
wakeups from originator to target.

Thans,

	Ingo
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