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

Török Edwin
2008-10-22T17:25:47Z

On 2008-10-22 20:22, Peter Zijlstra wrote:
> On Wed, 2008-10-22 at 17:48 +0200, Ingo Molnar wrote:
>
>> * 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?
>>
>
> Yes, I've already suggested this. Use the exact same hooks that
> lockdep/lockstat use.

Ok, I'll work on this when I get some time :)
[hopefully this weekend test the 'contend with points patch', next
weekend write the new tracepoints]

Best regards,
--Edwin