linux-kernel - Re: perf: prctl(PR_TASK_PERF_EVENTS

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Message-ID: <20120130113115.GA6565@elte.hu>
Date:	Mon, 30 Jan 2012 12:31:15 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Frédéric Weisbecker <fweisbec@...il.com>,
	Andrew Steets <asteets@...advisors.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: perf: prctl(PR_TASK_PERF_EVENTS_DISABLE) has no effect


* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> On Mon, 2012-01-30 at 11:11 +0100, Ingo Molnar wrote:
> > So, what workflow are you suggesting to Andrew?
> 
> Librarize perf record, then in your code do something like:
> 
> #include "perf_record.h"

Maybe. (and then it shouldnt be limited to perf_record.h but 
should be events.h plus libevents.so or such)

> 
>   handle = perf_record_init(); /* creates perf events and creates
>                                   a record thread that writes samples
>                                   to perf.data, consumes env(PERF_*)
>                                   for configuration, registers with
>                                   at_exit() for cleanup */
>   if (!handle)
>     /* burn */
> 
>   /* do you other code */
> 
>   perf_record_start(handle);
> 
>   /* do the bit you want profiled */
> 
>   perf_record_stop(handle);
> 
> Then build with -lperfrecord or so. Not too hard, right?

Isnt a simple prctl() so much easier and faster?

What's your concern with the prctl()? This would arguably be the 
right kind of usage for prctl(): it's an established API/ABI for 
process/task-wide settings.

Thanks,

	Ingo
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