linux-kernel - Re: [PATCH 3/4] perf tools: Fix probing the kernel API with cpu-wide events

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Message-ID: <53EAFCED.8030206@intel.com>
Date:	Wed, 13 Aug 2014 08:51:41 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Namhyung Kim <namhyung@...il.com>
CC:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 3/4] perf tools: Fix probing the kernel API with cpu-wide
 events

On 08/13/2014 08:37 AM, Namhyung Kim wrote:
> On Tue, 12 Aug 2014 18:04:30 +0300, Adrian Hunter wrote:
>> Fall back to probing with the current pid if cpu-wide
>> probing fails.  This primarily affects the setting of
>> comm_exec flag when the user is un-privileged and
>> /proc/sys/kernel/perf_event_paranoid > 0.  The change
>> to comm_exec can be observed by using -vv with
>> perf record and a kernel that supports comm_exec.
> 
> Maybe I'm missing something - why not just try process-wide probing in
> the first place?

Same reason as patch 4 i.e. to avoid a jump label change when doing
system-wide tracing.

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