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https://issues.apache.org/jira/browse/CASSANDRA-4937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13549155#comment-13549155
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Jonathan Ellis commented on CASSANDRA-4937:
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bq. Practice shows that kernel is pretty efficient on reclaiming once used
pages, when in need, and we still have writer that skips cache
Shouldn't we just take out cache-skipping on [C]RAR entirely then?
bq. I have actually experimented with preheating rows is we have
compaction_preheat_key_cache enabled
Why does this work better than the old mincore approach we tried?
> CRAR improvements (object cache + CompressionMetadata chunk offset storage
> moved off-heap).
> -------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-4937
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4937
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Pavel Yaskevich
> Assignee: Pavel Yaskevich
> Fix For: 1.2.1
>
> Attachments: CASSANDRA-4937.patch
>
>
> After good amount of testing on one of the clusters it was found that in
> order to improve read latency we need to minimize allocation rate that
> compression involves, that minimizes GC (as well as heap usage) and
> substantially decreases latency on read heavy workloads.
> I have also discovered that RAR skip cache harms performance in situation
> when reads are done in parallel with compaction working with relatively big
> SSTable files (few GB and more). The attached patch removes possibility to
> skip cache from compressed files (I can also add changes to RAR to remove
> skip cache functionality as a separate patch).
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