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https://issues.apache.org/jira/browse/CASSANDRA-21134?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sam Lightfoot updated CASSANDRA-21134:
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Description:
Follow-up from the implementation for compaction reads (CASSANDRA-19987)
Notable points
* Update the start-up check that impacts DIO writes
({_}checkKernelBug1057843{_})
* RocksDB uses 1 MB flush buffer. This should be configurable and performance
tested (256KB vs 1MB)
* Introduce compaction_write_disk_access_mode
was:
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.
> Direct IO support for compaction writes
> ---------------------------------------
>
> Key: CASSANDRA-21134
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21134
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: Local/Compaction
> Reporter: Sam Lightfoot
> Assignee: Sam Lightfoot
> Priority: Normal
> Fix For: 5.x
>
>
> Follow-up from the implementation for compaction reads (CASSANDRA-19987)
> Notable points
> * Update the start-up check that impacts DIO writes
> ({_}checkKernelBug1057843{_})
> * RocksDB uses 1 MB flush buffer. This should be configurable and
> performance tested (256KB vs 1MB)
> * Introduce compaction_write_disk_access_mode
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