Jon Haddad created CASSANDRA-19987:
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Summary: Use direct IO for compaction reads
Key: CASSANDRA-19987
URL: https://issues.apache.org/jira/browse/CASSANDRA-19987
Project: Cassandra
Issue Type: Improvement
Components: Local/Compaction
Reporter: Jon Haddad
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.
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