From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Frédéric Weisbecker" <fweisbec@gmail.com>,
"Andrew Steets" <asteets@rgmadvisors.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
"Paul Mackerras" <paulus@samba.org>,
"Arnaldo Carvalho de Melo" <acme@ghostprotocols.net>
Subject: Re: perf: prctl(PR_TASK_PERF_EVENTS_DISABLE) has no effect
Date: Mon, 30 Jan 2012 14:58:36 +0100 [thread overview]
Message-ID: <20120130135836.GA5703@elte.hu> (raw)
In-Reply-To: <1327931107.2446.205.camel@twins>
* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > 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.
>
> Its doing things backwards, [...]
What does that mean?
> [...] also the whole concept of allowing people to hide things
> from a profiler is so rotten I'm not willing to even consider
> the notion.
But what we want here is not to hide things from the profiler,
what we want to be able to is to *ask* the profiler to hide
things for us, and we do that for a good reason.
This distinction (which I agree is important) could be
implemented by adding a "allow self-profiling" bit (default
disabled) in the perf_attr. That way such code would not be able
to 'hide' from a simple:
perf top
perf record -a
session, but would be able to self-profile from such a session:
perf record --allow-self-profile ...
where there could be some easy shortcut for
--allow-self-profile, such as:
perf record -S
that way no code could ever hide from a profiler, only if the
profiler is specifically allowing self-profiling. (opt in)
The librarization you suggested might make sense too - but i
think people will gravitate towards the easier to use variant,
and prctl() is as easy and straightforward as it gets.
We can Cc: it to Linus with an explicit [RFC] and he can shoot
it down if the API is ugly - but I don't think it's ugly.
Hm?
Thanks,
Ingo
next prev parent reply other threads:[~2012-01-30 13:59 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-27 17:03 perf: prctl(PR_TASK_PERF_EVENTS_DISABLE) has no effect Andrew Steets
2012-01-27 17:12 ` Peter Zijlstra
2012-01-27 20:06 ` Andrew Steets
2012-01-27 21:34 ` Peter Zijlstra
2012-01-28 12:01 ` Ingo Molnar
2012-01-28 23:48 ` Andrew Steets
2012-01-29 16:32 ` Ingo Molnar
2012-01-29 17:50 ` Gleb Natapov
2012-01-30 9:52 ` Peter Zijlstra
2012-01-30 10:11 ` Ingo Molnar
2012-01-30 11:01 ` Peter Zijlstra
2012-01-30 11:31 ` Ingo Molnar
2012-01-30 13:45 ` Peter Zijlstra
2012-01-30 13:58 ` Ingo Molnar [this message]
2012-01-30 15:30 ` Arnaldo Carvalho de Melo
2012-01-30 15:29 ` Arnaldo Carvalho de Melo
2012-02-01 19:03 ` Frederic Weisbecker
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