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Paulo Motta commented on CASSANDRA-16436: ----------------------------------------- Thanks. I added some minor follow-up review changes on [this PR|https://github.com/subkanthi/cassandra/pull/1/files] to your branch. Let me know what do you think. I tested the patch locally on a docker image and got the expected message when there is a high read_ahead_kb setting: {noformat} WARN [main] 2022-01-02 19:54:25,030 StartupChecks.java:358 - Detected high '/sys/block/vda/queue/read_ahead_kb' setting of 4096 for device '/dev/vda1' of data directory '/opt/cassandra/data/data'. It is recommended to set this value to 8(KB) on SSDs or 64(KB) on HDDs to prevent excessive IO usage and page cache churn on read-intensive workloads. {noformat} I checked the warning is not print when the read_ahead_kb setting is below 128KB. Final patch and CI: |[trunk|https://github.com/apache/cassandra/compare/trunk...pauloricardomg:subkanthi/16436-trunk-rebased]|[tests|https://ci-cassandra.apache.org/view/patches/job/Cassandra-devbranch/1342/]| > Add startup check for large read_ahead_kb setting > ------------------------------------------------- > > Key: CASSANDRA-16436 > URL: https://issues.apache.org/jira/browse/CASSANDRA-16436 > Project: Cassandra > Issue Type: Improvement > Components: Local/Startup and Shutdown > Reporter: Paulo Motta > Assignee: Kanthi Subramanian > Priority: Normal > Labels: AdventCalendar2021, lhf > > A well known production tuning recommendation is to dial back the > {{read_ahead_kb}} Linux setting from the default of 4096 in most > distributions as this can cause high IO usage and cache churn on > read-intensive workloads. > We should add a startup warning to detect when a high {{read_ahead_kb}} is > used and recommend the user to dial back to a reasonable value, which varies > according to the workload but a general guideline is to tune this to 8kb. -- This message was sent by Atlassian Jira (v8.20.1#820001) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org