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Date: Fri, 3 Jul 2009 11:41:47 -0700 (PDT)
From: "stack (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Updated: (HBASE-1597) Prevent unnecessary caching of blocks
 during compactions
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     [ https://issues.apache.org/jira/browse/HBASE-1597?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

stack updated HBASE-1597:
-------------------------

      Resolution: Fixed
    Hadoop Flags: [Reviewed]
          Status: Resolved  (was: Patch Available)

Patch looks good. Tested it with upload. Logs look fine. Committing.... (Rolled up lrublockcache stats logging into one log message instead of 3 as part of commit). 

> Prevent unnecessary caching of blocks during compactions
> --------------------------------------------------------
>
>                 Key: HBASE-1597
>                 URL: https://issues.apache.org/jira/browse/HBASE-1597
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.20.0
>            Reporter: Jonathan Gray
>            Assignee: Jonathan Gray
>             Fix For: 0.20.0
>
>         Attachments: HBASE-1597-v1.patch, HBASE-1597-v2.patch
>
>
> When running any kind of compaction, we read every block of every storefile being compacted into the block cache.
> We would like to reuse any already cached blocks, if available, but otherwise we should not bog down the LRU with unnecessary blocks.
> This is not as bad as it was with the old LRU because the latest LRU implementation (HBASE-1460) is scan-resistant.  This ensures that we are not causing massive eviction of the blocks that are being read multiple times or from in-memory tables.  However, this does add to the GC-woes of an import because each block gets further referenced, and for longer periods of time.  There is also overhead in running the LRU evictions.

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