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

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Message-ID: <4F554DC7.8010504@fb.com>
Date:	Mon, 5 Mar 2012 15:35:35 -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

Like you probably figured from my other mail, we deal with deeply nested 
callchains with unwieldy function names a lot -- thanks to C++ and 
template programming. --tui's collapsing/expanding functionality is 
quite useful to navigate that mess. I'm just taking this opportunity to 
get some attention focused on improving it :)

On 3/5/12 2:26 PM, Arnaldo Carvalho de Melo wrote:

>> Here's an example:
>>
>> # perf record -ag -- sleep 3
>> # perf report -G -s pid --tui # SIGSEGV
>
> Ok, now this is a good report, I managed to reproduce and will work on a
> fix, thanks,

Something like this seems to do it for me.

         offset = addr - sym->start;
+       len = sym->end - sym->start;
+       if (offset >= len)
+               return 0;
+

The other problem area seems to be callchains when using -p regexp -x 
options. I'll try to summarize problems there in a separate thread.

  -Arun
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