Messages in this thread | | | Date | Mon, 30 Jan 2012 11:11:21 +0100 | From | Ingo Molnar <> | Subject | Re: 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
| |