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From "Shrijeet Paliwal (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5898) Consider double-checked locking for block cache lock
Date Thu, 13 Dec 2012 22:22:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13531575#comment-13531575
] 

Shrijeet Paliwal commented on HBASE-5898:
-----------------------------------------

Lars, we saw this twice in two days (once each day, on different region servers).
It was been 36 hours since we put -XX:+UseMembar back & restarted region servers, have
not seen again yet.

Stack documented this as part of HBASE-3622, http://hbase.apache.org/book/trouble.rs.html


                
> 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.

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