linux-kernel - Re: [RFC PATCH] perf: Add PERF_RECORD_SWITCH to indicate context switches

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Message-ID: <1434115713.1484.9.camel@arm.com>
Date:	Fri, 12 Jun 2015 14:28:33 +0100
From:	Pawel Moll <pawel.moll@....com>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	"mathieu.poirier@...aro.org" <mathieu.poirier@...aro.org>
Subject: Re: [RFC PATCH] perf: Add PERF_RECORD_SWITCH to indicate context
 switches

On Fri, 2015-06-12 at 14:15 +0100, Adrian Hunter wrote:
> >>>> all 3 are already part of sample_id.
> >>>
> >>> You have to decide whether you expect to be able to use an event without
> >>> sample_id. MMAP and MMAP2 both have pid, tid which are in sample_id, LOST
> >>> has id, EXIT and FORK have time, all of the THROTTLE/UNTHROTTLE members are
> >>> in sample_id etc. So it currently looks like we expect to be able to use an
> >>> event without requiring sample_id.
> > 
> > The fact that there is this duplication is because sample_id_all came
> > after those events, but this new one being proposed doesn't have to do
> > it :-)
> 
> Thanks, that's clear then.  There will just need to be a flag to indicate
> whether it is scheduling in or out.

Just a thought: wouldn't it be good to know what CPU have we been
scheduled from/to? This kind of information would be especially valuable
in heterogeneous systems.

Pawel

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