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https://issues.apache.org/jira/browse/CASSANDRA-6919?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13978020#comment-13978020
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Benedict commented on CASSANDRA-6919:
-------------------------------------
Split out 7073 and pushed -f with those changes removed
> Use OpOrder to guard sstable references for reads, instead of
> acquiring/releasing references
> --------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-6919
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6919
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Benedict
> Assignee: Benedict
> Priority: Minor
> Labels: performance
> Fix For: 2.1 beta2
>
>
> To slightly improve CASSANDRA-6916, and because it's a bit of a
> simplification anyway, we should move to ensuring sstable resources remain
> around during reads by guarding them with an OpOrder (which is also being
> introduced for CASSANDRA-6694) instead of using markReferenced()/release.
> Note this does not eliminate markReferenced, as for long running processes
> such as compaction it makes sense to have an independent mechanism, because
> these long running processes would prevent all resource cleanup for their
> duration rather than just the resources they're using.
> All this does is cleanup and slightly optimise the read path, whilst giving
> better guarantees about resource cleanup (e.g. page cache dropping of old
> sstables which may have been replaced multiple times since the reader was
> created, so we are dropping pages we don't realise are still in use - in real
> terms it should be very rare for such a reader to outlive multiple
> replacements and this is only a performance issue, not a matter of
> correctness, but it's nice to absolutely be certain anyway).
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