linux-kernel - Re: [PATCH 1/5] perf tools: Fix -C option for record command

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Date:	Tue, 26 Feb 2013 15:38:38 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	David Ahern <dsahern@...il.com>, linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH 1/5] perf tools: Fix -C option for record command

On 02/25, Jiri Olsa wrote:
>
> On Mon, Feb 25, 2013 at 11:56:38AM -0700, David Ahern wrote:
>
> > If a target is given (-a, -C, -p or -t) that is what the data is
> > collected for -- all cpus, a cpu, or one or more task ids. The
> > workload in that case becomes a means for bounding the data
> > collection (start and end points).

OK, so I misunderstood the intent and misread the code. Thanks
David.

> yes, that's what actually this patch fixies.. now you can run:
>
>   perf record -C 0 ls
>
> and that will attach to cpu 0 only (same as '-a -C 0' before)

Yes, and thus this is consistent with -a and correct. Thanks and
sorry for noise.


But,

> maybe we could consider having:
>
>   perf record -C 0 ls
>     - attaching to CPU 0 and ls workload pid
>
>   perf record -a -C 0 ls
>     - attaching to CPU 0 globaly

Can't really comment since I am not a perf user, but imho looks good.

And useful. And least this behaviour was useful to me when I tried
to test the perf/uprobe changes.

Oleg.

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