Migrate cached pages during compaction
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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
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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