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Ryan McGuire edited comment on CASSANDRA-8342 at 11/25/14 11:57 PM: -------------------------------------------------------------------- http://riptano.github.io/cassandra_performance/graph_v4/graph.html?stats=stats.8342.json Definitely agree that increasing it doesn't improve things, but not seeing much of a dropoff either. Per Jonathan's suggestion, this test was with load smaller than memory. Rereading the guidance text in the yaml, it would seem to suggest testing this with a load larger than memory? was (Author: enigmacurry): http://riptano.github.io/cassandra_performance/graph_v4/graph.html?stats=stats.8342.json Definitely agree that increasing it doesn't improve things, but not seeing much of a dropoff either. Per Jonathan's suggestion, this test was with load smaller than memory. Rereading the guidance text in the yaml, it would seem to suggest testing this with a load larger? > Remove historical guidance for concurrent reader and writer tunings. > -------------------------------------------------------------------- > > Key: CASSANDRA-8342 > URL: https://issues.apache.org/jira/browse/CASSANDRA-8342 > Project: Cassandra > Issue Type: Improvement > Reporter: Matt Stump > Assignee: Ryan McGuire > > 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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)