linux-kernel - Re: [PATCH] perf: make perf report -D print sampled CPU

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Date:	Fri, 28 May 2010 15:03:15 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Arnaldo Carvalho de Melo <acme@...radead.org>
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	paulus@...ba.org, davem@...emloft.net, fweisbec@...il.com,
	perfmon2-devel@...ts.sf.net, eranian@...il.com, tzanussi@...il.com,
	Arun Sharma <aruns@...gle.com>
Subject: Re: [PATCH] perf: make perf report -D print sampled CPU

On Fri, May 28, 2010 at 2:57 PM, Arnaldo Carvalho de Melo
<acme@...radead.org> wrote:
> Em Fri, May 28, 2010 at 12:08:01PM +0200, Stephane Eranian escreveu:
>> It is useful to know on which CPU a sample was captured on.
>> The information is captured with perf record -R but it was
>> not printed out by perf report -D. This patch adds this.
>>
>> When -R is not used, cpu is set to -1to indicate that
>> the CPU is unknown (it is not captured).
>>
>> Signed-off-by: Stephane Eranian <eranian@...gle.com>
>
> It conflicts with Arun's patch for sorting by CPU that I started playing with
> yesterday, but in a good way, i.e. printing the CPU at that dump_printf spot
> was one of the changs I made in Arun's patch as well.
>
Yes, I realized that afterwards.

> [root@...lia linux-2.6-tip]# perf report -D | grep SAMPLE | head -6
> 0x10240 [0x28]: PERF_RECORD_SAMPLE(IP, 1): 2 17252/17252: 0xffffffff81253362 period: 1894446
> 0x10268 [0x28]: PERF_RECORD_SAMPLE(IP, 1): 2 17252/17252: 0xffffffff81253338 period: 1894446
> 0x10290 [0x28]: PERF_RECORD_SAMPLE(IP, 1): 2 17252/17252: 0xffffffff8125300d period: 1905103
> 0x102b8 [0x28]: PERF_RECORD_SAMPLE(IP, 1): 0 0/0: 0xffffffff8109117d period: 1838260
> 0x102e0 [0x28]: PERF_RECORD_SAMPLE(IP, 1): 0 293/293: 0xffffffff8101ace6 period: 352697
> 0x10308 [0x28]: PERF_RECORD_SAMPLE(IP, 1): 0 1763/1763: 0xffffffff8101ace6 period: 352697
> [root@...lia linux-2.6-tip]#
>
> I added it just before the pid/tid but prefixing it with "cpu: " is as good as
> doing it that way.
>
Fine. I think there needs to be some documenation explaining the structure
of the line here. I had to dig into the code to understand it.

> I'm applying both patches after some tests,
>
Thanks.
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