Hi Sage, Yes, I totally understand bluestore did much more things than a raw disk, but the current overhead is a little too big to our usage. I will compare bluestore with XFS(also has metadata tracking, allocation, and so on), and to see if XFS also has such impact. I would like to give a flamegraph later, but from the perfcounter, we could find most of time were spent in "kv_lat". For FTL, yes, it is a good idea, after we get the flame graph, we could discuss which part could be improved by FTL, firmware, even open channel. 2017-07-12 20:02 GMT+08:00 Sage Weil <sage@xxxxxxxxxxxx>: > On Wed, 12 Jul 2017, 攀刘 wrote: >> Hi Cephers, >> >> I did some experiment today to compare the latency between one >> P3500(2T nvme SSD) and bluestore(fio + libfio_objectstore.so): >> >> For iodepth = 1, the random write latency of bluestore is 276.91us, >> compare with 14.71 of SSD, big overhead. >> >> I also test iodepth = 16, Still, there is a big overhead.(143 us -> 642 us) >> >> What is your opinion? > > There is a lot of work that bluestore is doing over the raw device as it > is implementing all of the metadata tracking, checksumming, allocation, > and so on. There's definitely lots of room for improvement, but I'm > not sure you can expect to see latencies in the 10s of us. That said, it > would be interesting to see an updated flamegraph to see where the time is > being spent and where we can slim this down. On a new nvme it's possible > we can do away with some of the complexity of, say, the allocator, since > the FTL is performing a lot of the same work anyway. > > sage -- 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
