Re: perf: prctl(PR_TASK_PERF_EVENTS_DISABLE) has no effect

From: Peter Zijlstra
Date: Mon Jan 30 2012 - 04:52:51 EST


On Sun, 2012-01-29 at 17:32 +0100, Ingo Molnar wrote:
> * Andrew Steets <asteets@xxxxxxxxxxxxxxx> wrote:
>
> > On 1/28/12 6:01 AM, Ingo Molnar wrote:
> >
> > >> prctl(PR_TASK_PERF_EVENTS_DISABLE) doesn't appear to
> > >> disable perf event counters. Here is a demonstration
> > >> program:
> > >
> > > btw., what's your usecase?
> >
> > I'm trying to profile a small section of a long-running
> > program. I ran into trouble using call-graph recording and I
> > thought this might be an alternative way of getting what I was
> > after.
>
> That usecase indeed makes sense. Peter, could we allow this for
> privileged tasks, depending on the perf_paranoia settings or
> such?

I really dislike it. The sane way around this would be to allow easy
self-profiling instead of doing things arse about face like that.
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