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Jean-Daniel Cryans commented on HBASE-5898: ------------------------------------------- A not too scientific comparison. Before: total=6.26 GB, free=1.04 GB, max=7.3 GB, blocks=101753, accesses=5078311, hits=4333154, hitRatio=85.32%, cachingAccesses=5078311, cachingHits=4333154, cachingHitsRatio=85.32%, evictions=54, evicted=643404, evictedPerRun=11914.888671875 After: total=6.45 GB, free=878.07 MB, max=7.3 GB, blocks=104747, accesses=5810869, hits=4345850, hitRatio=74.78%, cachingAccesses=5810869, cachingHits=4345850, cachingHitsRatio=74.78%, evictions=52, evicted=627755, evictedPerRun=12072.2119140625 This is using the benchmark tool I'm working on right now, I had to port Todd's patch since I'm not going through the HFile code but I'm doing exactly what he does. The test is started completely cold. It uses 5 threads. The big takeout is that it did 14% more cache accesses which had the side effect of lowering the hit ratio. The number of actual cache hits was a big higher. > Consider double-checked locking for block cache lock > ---------------------------------------------------- > > Key: HBASE-5898 > URL: https://issues.apache.org/jira/browse/HBASE-5898 > Project: HBase > Issue Type: Improvement > Components: performance > Affects Versions: 0.94.1 > Reporter: Todd Lipcon > Assignee: Todd Lipcon > Priority: Critical > Attachments: 5898-TestBlocksRead.txt, hbase-5898.txt > > > Running a workload with a high query rate against a dataset that fits in > cache, I saw a lot of CPU being used in IdLock.getLockEntry, being called by > HFileReaderV2.readBlock. Even though it was all cache hits, it was wasting a > lot of CPU doing lock management here. I wrote a quick patch to switch to a > double-checked locking and it improved throughput substantially for this > workload. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira