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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5898) Consider double-checked locking for block cache lock
Date Fri, 26 Oct 2012 06:03:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13484734#comment-13484734
] 

ramkrishna.s.vasudevan commented on HBASE-5898:
-----------------------------------------------

We have recently hit this issue.. My major concern here is there is contention only happening
right?  But here in our case the scan itself did not happen for almost 10 mins?
The thread dump clearly says what was found over in this JIRA.
                
> 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-TestBlocksRead.txt, HBASE-5898-0.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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