Hi Sam/Sage,
As we discussed earlier, enabling the present OpTracker code degrading performance severely. For example, in my setup a single OSD node with 10 clients is reaching ~103K read iops with io served from memory while optracking is disabled but enabling optracker it is reduced to ~39K iops. Probably, running OSD without enabling OpTracker is not an option for many of Ceph users.
Now, by sharding the Optracker:: ops_in_flight_lock (thus xlist ops_in_flight) and removing some other bottlenecks I am able to match the performance of OpTracking enabled OSD with OpTracking disabled, but with the expense of ~1 extra cpu core.
In this process I have also fixed the following tracker.

http://tracker.ceph.com/issues/9384


and probably http://tracker.ceph.com/issues/8885 too.



I have created following pull request for the same. Please review it.



https://github.com/ceph/ceph/pull/2440



Thanks & Regards

Somnath


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