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https://issues.apache.org/jira/browse/CASSANDRA-1902?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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T Jake Luciani updated CASSANDRA-1902:
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Description:
Post CASSANDRA-1470 there is an opportunity to migrate cached pages from a
pre-compacted CF during the compaction process. This is now important since
CASSANDRA-1470 caches effectively nothing.
For example an active CF being compacted hurts reads since nothing is cached in
the new SSTable.
The purpose of this ticket then is to make sure SOME data is cached from active
CFs. This can be done my monitoring which Old SSTables are in the page cache
and caching active rows in the New SStable.
A simpler yet similar approach is described here:
http://insights.oetiker.ch/linux/fadvise/
was:
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/
> 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: 0.8
>
> Attachments:
> 0001-CASSANDRA-1902-cache-migration-impl-with-config-option.txt,
> 1902-formatted.txt, 1902-per-column-migration-rebase2.txt,
> 1902-per-column-migration.txt, CASSANDRA-1902-v3.patch
>
> Original Estimate: 32h
> Time Spent: 56h
> Remaining Estimate: 0h
>
> Post CASSANDRA-1470 there is an opportunity to migrate cached pages from a
> pre-compacted CF during the compaction process. This is now important since
> CASSANDRA-1470 caches effectively nothing.
> For example an active CF being compacted hurts reads since nothing is cached
> in the new SSTable.
> The purpose of this ticket then is to make sure SOME data is cached from
> active CFs. This can be done my monitoring which Old SSTables are in the page
> cache and caching active rows in the New SStable.
> A simpler yet similar approach is described here:
> http://insights.oetiker.ch/linux/fadvise/
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