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

Ingo Molnar
2008-10-22T15:49:17Z

* Török Edwin <edwintorok@gmail.com> 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?

Ingo