linux-kernel - Re: [PATCH] perf report: auto-detect branch stack sampling mode

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Message-ID: <4F55337B.4080807@fb.com>
Date:	Mon, 5 Mar 2012 13:43:23 -0800
From:	Arun Sharma <asharma@...com>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>
CC:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Stephane Eranian <eranian@...gle.com>,
	<linux-kernel@...r.kernel.org>, <dsahern@...il.com>,
	<ravitillo@....gov>, <khandual@...ux.vnet.ibm.com>,
	<robert.richter@....com>, <ming.m.lin@...el.com>,
	<vweaver1@...s.utk.edu>, <andi@...stfloor.org>
Subject: Re: [PATCH] perf report: auto-detect branch stack sampling mode

On 3/5/12 12:35 PM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 05, 2012 at 05:30:33PM +0100, Peter Zijlstra escreveu:
>> On Mon, 2012-03-05 at 16:56 +0100, Ingo Molnar wrote:
>>> A third usability bug is that for some reason a branch sampling
>>> 'perf report' defaults to the stdio output on my testsystem -
>>> with --no-branch-stack it gives the regular tui.
>
>> Ah, I would not have noticed that since I still explicitly build my perf
>> without TUI support. That stuff mostly just gets in the way.
>
> Do you have any specific complaints about it?
>

I think --tui code paths have some bugs that cause it to SIGSEGV, while 
the --stdio paths don't. I think much of it has to do with how often 
that particular combination of command line options is used.

Here's an example:

# perf record -ag -- sleep 3
# perf report -G -s pid --tui # SIGSEGV
# perf report -G -s pid --stdio # works fine

Details attached.

  -Arun




View attachment "perf-debug.txt" of type "text/plain" (4717 bytes)