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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (HBASE-7336) HFileBlock.readAtOffset does not work well with multiple threads
Date Mon, 17 Dec 2012 22:14:17 GMT

     [ https://issues.apache.org/jira/browse/HBASE-7336?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lars Hofhansl resolved HBASE-7336.
----------------------------------

    Resolution: Fixed

I reapplied the patch.
(the other anomaly of this test is that all data fits into a single HDFS block, so of course
seek+read will be favored here)
                
> HFileBlock.readAtOffset does not work well with multiple threads
> ----------------------------------------------------------------
>
>                 Key: HBASE-7336
>                 URL: https://issues.apache.org/jira/browse/HBASE-7336
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>            Priority: Critical
>             Fix For: 0.96.0, 0.94.4
>
>         Attachments: 7336-0.94.txt, 7336-0.96.txt
>
>
> HBase grinds to a halt when many threads scan along the same set of blocks and neither
read short circuit is nor block caching is enabled for the dfs client ... disabling the block
cache makes sense on very large scans.
> It turns out that synchronizing in istream in HFileBlock.readAtOffset is the culprit.

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