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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Updated: (CASSANDRA-1902) Migrate cached pages during compaction
Date Fri, 24 Dec 2010 21:06:45 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-1902?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis updated CASSANDRA-1902:
--------------------------------------

    Fix Version/s: 0.7.1

> Migrate cached pages during compaction 
> ---------------------------------------
>
>                 Key: CASSANDRA-1902
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1902
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.7.1
>            Reporter: T Jake Luciani
>            Assignee: T Jake Luciani
>             Fix For: 0.7.1
>
>
> Post CASSANDRA-1470 there is an opportunity to migrate cached pages from a pre-compacted
CF during the compaction process.  
> First, add a method to MmappedSegmentFile: long[] pagesInPageCache() that uses the posix
mincore() function to detect the offsets of pages for this file currently in page cache.
> Then add getActiveKeys() which uses underlying pagesInPageCache() to get the keys actually
in the page cache.
> use getActiveKeys() to detect which SSTables being compacted are in the os cache and
make sure the subsequent pages in the new compacted SSTable are kept in the page cache for
these keys. This will minimize the impact of compacting a "hot" SSTable.
> A simpler yet similar approach is described here: http://insights.oetiker.ch/linux/fadvise/

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