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Mulugeta Mammo commented on CASSANDRA-14466: -------------------------------------------- The results we posted are based on a read_ahead_kb value of 8, a chunk size of 64KB and a uniform distribution invocation: {{cassandra-stress user profile=$CASSANDRA_TOOLS/cqlstress-insanity-example.yaml ops\(simple1=1\) no-warmup cl=ONE duration=300s -mode native cql3 -pop dist=uniform\(1..1200000000\) -node server_ip -rate threads=288}} And no we don’t see any significant difference if we set the read_ahead_kb to 0. For a buffered run with read_ahead_kb set to 0 vs 8, we observed just a 5% increase in throughput for the 0. Also, for all of our runs, the Cassandra caches (row cache, key cache, etc.) were disabled. For a cacheable data, we believe a better solution is to have the caches enabled and tuned instead of relying on the page cache. Generally, we believe relying on the page cache is not a good strategy as the application has no control over the caching. The problem also gets worse if other applications, e.g. a Spark analytics workload, are running on the same node. You may download and test it, git clone -b direct_io [https://github.com/mulugetam/cassandra.git] (requires JDK 10) > Enable Direct I/O > ------------------ > > Key: CASSANDRA-14466 > URL: https://issues.apache.org/jira/browse/CASSANDRA-14466 > Project: Cassandra > Issue Type: New Feature > Components: Local Write-Read Paths > Reporter: Mulugeta Mammo > Priority: Major > Attachments: direct_io.patch > > > Hi, > JDK 10 introduced a new API for Direct IO that enables applications to bypass > the file system cache and potentially improve performance. Details of this > feature can be found at [https://bugs.openjdk.java.net/browse/JDK-8164900]. > This patch uses the JDK 10 API to enable Direct IO for the Cassandra read > path. By default, we have disabled this feature; but it can be enabled using > a new configuration parameter, enable_direct_io_for_read_path. We have > conducted a Cassandra read-only stress test and measured a throughput gain of > up to 60% on flash drives. > The patch requires JDK 10 Cassandra Support - > https://issues.apache.org/jira/browse/CASSANDRA-9608 > Please review the patch and let us know your feedback. > Thanks, > [^direct_io.patch] > -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org