I didn't know about mutrace, thanks for that reference!

On Tue, Sep 30, 2014 at 8:13 PM, Milosz Tanski <[email protected]> wrote:
> On Tue, Sep 30, 2014 at 7:36 PM, Noah Watkins <[email protected]> 
> wrote:
>> On Tue, Sep 30, 2014 at 10:42 AM, Somnath Roy <[email protected]> 
>> wrote:
>>> Also, I don't think this lock has big impact to performance since it is 
>>> already sharded to index level. I tried with reader/writer implementation 
>>> of this lock (logic will be somewhat similar to your state concept) and not 
>>> getting any benefit .
>>
>> If there is interest in identifying locks that are introducing latency
>> it might useful to add some tracking features to Mutex and RWLock. A
>> simple thing would be to just record maximum wait times per lock and
>> dump this via admin socket.
>
> Noah,
>
> You're better off running some kind of synthetic test using mutrace
> (you can't use tcmalloc/jemalloc) or measuring futex syscalls via a
> pref tracepoint. Generally adding this kind of tracking into the locks
> itself ends up being even more expensive.
>
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>
>
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