[jira] [Commented] (HBASE-17057) Minor compactions should also drop page cache behind reads

["Gary Helmling (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-17057?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15849235#comment-15849235 ] 

Gary Helmling commented on HBASE-17057:
---------------------------------------

Since this is now based on configuration rather than overloading the compaction policy throttle threshold, the configuration keys need to be added to hbase-default.xml with a description.

It's also worth pointing out that defaulting to true for this on minor compactions is a change in behavior, which is questionable for a point release (if this goes in to 1.3.1), though I'm not sure when you would want the old behavior.

Can you double check that this actually is effective on master?  Looking at StoreFileScanner.getScannersForStoreFiles (line 126), I see canUseDrop as a param, but don't see it used anywhere...

> Minor compactions should also drop page cache behind reads
> ----------------------------------------------------------
>
>                 Key: HBASE-17057
>                 URL: https://issues.apache.org/jira/browse/HBASE-17057
>             Project: HBase
>          Issue Type: Improvement
>          Components: Compaction
>            Reporter: Ashu Pachauri
>            Assignee: Ashu Pachauri
>             Fix For: 1.3.1
>
>         Attachments: HBASE-17057.V1.patch
>
>
> Long compactions currently drop cache behind reads/writes so that they don't pollute the page cache but short compactions don't do that. The bulk of the data is actually read during minor compactions instead of major compactions,  and thrashes the page cache since it's mostly not needed. 
> We should drop page cache behind minor compactions too. 



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