lkml.org 
[lkml]   [2012]   [Jan]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: perf: prctl(PR_TASK_PERF_EVENTS_DISABLE) has no effect

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

> On Sun, 2012-01-29 at 17:32 +0100, Ingo Molnar wrote:
> > * Andrew Steets <asteets@rgmadvisors.com> 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.

So, what workflow are you suggesting to Andrew?

I guess we are also hurting from the lack of dwarf stack
backtrace decoding - that would allow the filtering by parent
function without modifying the code. I think Frederic had a
prototype working for 32-bit - any update on that?

Andrew could work that problem around right now by adding:

-fno-omit-frame-pointer

to the build of the utility - that should activate -g and
perf-report's --parent filter should also work fine.

Thanks,

Ingo


\
 
 \ /
  Last update: 2012-01-30 11:13    [W:0.053 / U:5.872 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site