Matt Stump created CASSANDRA-8342:
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Summary: Remove historical guidance for concurrent reader and
tunings.
Key: CASSANDRA-8342
URL: https://issues.apache.org/jira/browse/CASSANDRA-8342
Project: Cassandra
Issue Type: Improvement
Reporter: Matt Stump
The cassandra.yaml and documentation provide guidance on tuning concurrent
readers or concurrent writers to system resources (cores, spindles). Testing
performed by both myself and customers demonstrates no benefit for thread pool
sizes above 64 in size, and for thread pools greater than 128 in size a
decrease in throughput. This is due to thread scheduling and synchronization
bottlenecks within Cassandra.
Additionally, for lower end systems reducing these thread pools provides very
little benefit because the bottleneck is typically moved to either IO or CPU.
I propose that we set the default value to 64 (current default is 32), and
remove all guidance/recommendations regarding tuning.
This recommendation may change in 3.0, but that would require further
experimentation.
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