Bluestore-Performance regression in the latest master

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Sage,
I am seeing the performance with the latest master is not stable compare to 3 days old master. The peak performance is higher but it is jumping up and down. Analyzing further I suspect recent cache changes has an impact. While the performance is high , I am seeing lower disk reads (probably because of cache hits) , but the low point is much lower when it is missing the cache probably. You were saying on the standup about adding buffers in the cache in the write path , is that merged into the master ?

The following pull request for cache that got merged seems reasonable.

https://github.com/ceph/ceph/pull/11295

Any hunch what is causing this degradation recently ? Otherwise, I need to dig down to find that out :-(

See the graph in the following link for the performance difference.

https://docs.google.com/spreadsheets/d/1JO3FaBbfT5jEdyYGB8EhHnAl5bAHe06ojLE85mPzsK4/edit?usp=sharing

The left side graph is with old master and right one is with latest master..Old one I ran for 10 hour and latest master I ran it for 2 hours.
The new one has *4X more* latency as well..

Thanks & Regards
Somnath



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