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

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Date:	Fri, 28 May 2010 15:44:31 +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 3:37 PM, Arnaldo Carvalho de Melo
<acme@...radead.org> wrote:
> Em Fri, May 28, 2010 at 03:03:15PM +0200, Stephane Eranian escreveu:
>> 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:
>> >> When -R is not used, cpu is set to -1to indicate that
>> >> the CPU is unknown (it is not captured).
>
>> > 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.
>
> Right, this so far is as ad-hoc as it can be :-)
>
> One idea that is in my TODO list is to generate some XML format people
> say that oprofile produces and there is also some other format that a
> valgrind tool uses that should be supported.
>
I think for a lot of people what matter is that the format be easily parseable
by Python/Perl scripts. XML may be fine too.

> I also plan to have it in a spreadsheet TUI widget, allowing lots of
> navigation gimmicks to help in debugging, like a popup that offers the
> list of mmaps for the thread where the sample below the cursor happened,
> etc.
You may get tons of data. Not sure you could manage interactively.
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