Re: [PATCH 4/4] Implement semaphore latency tracer

From: Ingo Molnar
Date: Wed Oct 22 2008 - 11:49:18 EST

* Török Edwin <edwintorok@xxxxxxxxx> wrote:

> On 2008-10-22 18:28, Ingo Molnar wrote:
> > hm, but the most common synchronization primitive are mutexes - and
> > those are not covered by your patchset.
> >
> Indeed. I've seen a patch from Jason Baron to introduce tracepoints
> for mutexes, but the conclusion was that the tracepoints should be in
> lockstat instead.
> And if lockstat is enabled Peter Zijlstra's 'contend with points'
> patch seems to do exactly what I want to.
> However I think it would be useful to have (a tracepoints based?)
> latency tracker, which can be enabled/disabled at runtime, and which
> doesn't add any data to the mutex/semaphore structures. My patchset
> was a first attempt towards that, but it seems that such use of
> tracepoints is not welcome at this time?
> Please tell me if I should continue working on this, or if I my
> patches are designed totally on the wrong way.

i think if you hook into Peter's lockstat APIs that should give us a
pretty good tracer, with no ugliness introduced. That would be rather
interesting. Peter, do you concur?

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