[jira] [Comment Edited] (CASSANDRA-8342) Remove historical guidance for concurrent reader and writer tunings.

["Ryan McGuire (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-8342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14225427#comment-14225427 ] 

Ryan McGuire edited comment on CASSANDRA-8342 at 11/25/14 11:57 PM:
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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?


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 all in memory though. Rereading the guidance text in the yaml would seem to suggest testing this with a load larger, no?

> 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.



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