On Fri, Feb 10, 2017 at 9:50 AM, LIU, Fei <james.liu@xxxxxxxxxxxxxxx> wrote: > With FIO single job queue depth 1(W/ vs W/O) , IOPS drop 3 times and > latency increased 3 times. As with more jobs, the IOPS drops more and > latency increase higher and higher. Assuming you have a random write workload, within a QD=1, it is entirely expected for the first write to the object to incur a performance penalty since it requires an additional round-trip operation to the backing OSDs. Since you only hit this penalty for the very first write to the object, its cost is amortized over future writes. This is similar to cloned images and the amortized cost of copying up the backing parent object to the clone on the first write. > The objectmap_locker in pre and post and objectmap update per IO really hurt > performance. Lockless queue and new way to caching objectmap? Any thoughts? By definition, with a QD=1, there is zero contention on that lock. The lock is really only held for a minuscule amount of time and is dropped while the OSD operation is in-progress. Do you actually have any performance metrics to back up this claim? Note that the post state is only hit when you issue a remove / trim / discard operation. -- Jason -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
