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

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Message-ID: <20140513112658.GX11096@twins.programming.kicks-ass.net>
Date:	Tue, 13 May 2014 13:26:58 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	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)

On Tue, May 13, 2014 at 07:10:02PM +0900, Dongsheng Yang wrote:
> On 05/13/2014 07:03 PM, Peter Zijlstra wrote:

> >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.
> 
> Ha, yes, indeed. In perf sched latency, we need to know the timestamp
> when a task enqueue and then we can calculate the delay time.
> So I want to take the use of success parameter in trace_sched_wakeup()
> to indicate that *this* wakeup did an enqueue.
> 
> But now I think it is okey if you really mind adding more tracepoints in
> scheduler. And I posted a patch after your patch in this thread to make
> perf sched latency work well.

I don't mind adding them per-se, as long as there's a reasonable effort
showing it doesn't slow down the wakeup-path.

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