[ https://issues.apache.org/jira/browse/HBASE-5898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13529612#comment-13529612 ]
Lars Hofhansl commented on HBASE-5898: -------------------------------------- Sorry... Missed the jstack there. I can see that all handlers are waiting to get the lock to load a block, but not where the lock is held. If HDFS is slow that would happen, if there was a deadlock that would also happen. I agree since it appears that all handlers are blocked this could be a deadlock. > 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 > Fix For: 0.94.3, 0.96.0 > > Attachments: 5898-0.94.txt, 5898-TestBlocksRead.txt, 5898-v2.txt, > 5898-v3.txt, 5898-v4.txt, 5898-v4.txt, HBASE-5898-0.patch, > HBASE-5898-1.patch, HBASE-5898-1.patch, 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 For more information on JIRA, see: http://www.atlassian.com/software/jira