[CASSANDRA-15452] investigate using POSIX_FADV_WILLNEED on compaction

• Type: Improvement
• Status: Open
• Priority: Normal
• Resolution: Unresolved
• Component/s: Legacy/Local Write-Read Paths, Local/Compaction
• Change Category: Performance
• Complexity: Normal
• Platform: All
• Assignee: Unassigned
• Reporter: Jon Haddad
• Created: 13/Dec/19 16:53
• Updated: 16/Dec/19 17:34

Description

On read heavy workloads Cassandra performs much better when using a low read ahead setting.   In my tests I've seen an 5x improvement in throughput and more than a 50% reduction in latency.  However, I've also observed that it can have a negative impact on compaction throughput. 

We should investigate using the POSIX_FADV_WILLNEED on files we're compacting to see if we can improve performance and reduce page faults.