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

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Date:	Tue, 6 Mar 2012 07:25:46 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Arun Sharma <asharma@...com>
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	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


* Arun Sharma <asharma@...com> wrote:

> Something like this seems to do it for me.
> 
>         offset = addr - sym->start;
> +       len = sym->end - sym->start;
> +       if (offset >= len)
> +               return 0;
> +

It would be nice to not have such inconsistent sym entries to 
begin with - i.e. to filter in the symbol code, not in the GUI 
front-end code.

> 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.

Btw., I have a text/regex filtering feature request there going 
beyond the issue of parent filtering, I often would love to be 
able to filter the sampled function itself:

  perf report sched

or:

  perf report time

or:

  perf report perf

to only see the list of (kernel) functions whose name name 
matches those patterns. (and skip all other functions)

Especially when I want to improve the tail portion of the 
profile this would be pretty useful. Today I can only do that 
with --stdio:

  perf report | grep sched

The -S option is too strict, it only allows individual symbols, 
no filters. Also, I hate typing '-S' ;-)

Thanks,

	Ingo
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