Direct I/O for Cassandra Compaction: Cutting p99 Read Latency by 5x (opens in new tab)

A patch I contributed to Apache Cassandra 6 cuts p99 read latency by 5x during compaction. Compaction pollutes the page cache with data the application knows is throwaway, but the kernel does not. Compaction is unavoidable, the price Cassandra pays for fast writes. Data isn't sorted on the way in;