[jira] [Created] (CASSANDRA-16072) Reduce thread contention in CommitLogSegment and HintsBuffer by rewriting CAS loops to atomic adds

["Michael Semb Wever (Jira)" <ji...@apache.org>]

Michael Semb Wever created CASSANDRA-16072:
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             Summary: Reduce thread contention in CommitLogSegment and HintsBuffer by rewriting CAS loops to atomic adds
                 Key: CASSANDRA-16072
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-16072
             Project: Cassandra
          Issue Type: Improvement
          Components: Consistency/Hints, Local/Commit Log
            Reporter: Michael Semb Wever
            Assignee: Michael Semb Wever


Follow up to CASSANDRA-15922

Both CommitLogSegment and HintsBuffer use AtomicIntegers for the current offset when allocating. Like in CASSANDRA\-15922 the loops on {{.compareAndSet(..)}} can be replaced with atomic adds using the {{. getAndAdd(..)}} method.

In highly contended environments the CAS failures can be high, starving writes in a running Cassandra node. On the same cluster CASSANDRA\-15922 was found, after CASSANDRA\-15922's fix was deployed, there was still problems around commit log flushing and hints. No flamegraph was collected that demonstrated the thread contention as clearly as was found in CASSANDRA\-15922, but the performance fix proposed here hopefully is obvious enough.



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