linux-kernel - Re: Adding a filter to events (instead of replacing one) was Re: [PATCH 1/2] perf, tools: Add PERF

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Date:	Wed, 1 Oct 2014 15:02:18 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Andi Kleen <andi@...stfloor.org>, jolsa@...hat.com,
	linux-kernel@...r.kernel.org, namhyung@...nel.org,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: Adding a filter to events (instead of replacing one) was Re:
 [PATCH 1/2] perf, tools: Add PERF_PID

On Wed, Oct 01, 2014 at 03:03:16PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Wed, Sep 24, 2014 at 01:51:08PM -0700, Andi Kleen escreveu:
> 
> > It's currently difficult to filter out perf itself using a filter.
> > This can give cascading effects during IO tracing when the IO perf
> > does itself causes more trace output.
>  
> > The best way to filter is to use the pid. But it's difficult to get the pid
> > of perf without using hacks.
>  
> > Add a PERF_PID meta variable to the perf filter that contains the current pid.
>  
> > With this patch the following works
>  
> > % perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...
> 
> So I tried this one now and saw the other patch, that applies the
> --filter to all events, while trying I got:

Patch seems reasonable to me.

However adding PERF_PID and sanitizing --filter are really two
different things and should probably not be mixed in a patch.

-Andi
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