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https://issues.apache.org/jira/browse/CASSANDRA-21094?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sam Lightfoot updated CASSANDRA-21094:
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Reviewers: (was: Ariel Weisberg, guo Maxwell)
> Use POSIX_FADV_SEQUENTIAL for SSTable reads during compaction and streaming
> ---------------------------------------------------------------------------
>
> Key: CASSANDRA-21094
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21094
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: Local/Compaction
> Reporter: Sam Lightfoot
> Assignee: Sam Lightfoot
> Priority: Normal
> Fix For: 5.x
>
>
> If we use direct io to read SSTables during compaction, we can avoid
> polluting the page cache with data we're about to delete. As another side
> effect, we also evict pages to make room for whatever we're putting in. This
> unnecessary churn leads to higher CPU overhead and can cause dips in client
> read latency, as we're going to be evicting pages that could be used to serve
> those reads.
> This is most notable with STCS as the SSTables get larger, potentially
> evicting the entire hot dataset out of cache, but is affected by every
> compaction strategy.
> This is a follow up to be done after CASSANDRA-15452 since we will have an
> internal buffer.
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