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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7907) Determine how many network threads we need for native transport
Date Wed, 10 Sep 2014 23:07:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14129314#comment-14129314
] 

Benedict commented on CASSANDRA-7907:
-------------------------------------

bq. I'd want some evidence that pinning to cores is going to give us a measurable benefit
before adding it to the code-base

bq. _We could even *try* pinning_....

Yes, we need to demonstrate an effect. But that is standard practice for performance enhancements
:-)

We have prior evidence that an effect will be seen, however. Not only from general practice
of having done this before in other contexts (including yourself), but [~jasobrown] has done
this on Cassandra, I believe as part of his investigations for CASSANDRA-4718, and seen an
effect.

> Determine how many network threads we need for native transport
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-7907
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7907
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Benedict
>            Priority: Minor
>
> With the introduction of CASSANDRA-4718, it is highly likely we can cope with just _one_
network IO thread. We could even try pinning it to a single (optionally configurable) core,
and (also optionally) pin all other threads to a different core, so that we can guarantee
extremely prompt execution (and if pinned to the correct core the OS uses for managing the
network, improve throughput further).
> Testing this out will be challenging, as we need to simulate clients from lots of IPs.
However, it is quite likely this would reduce the percentage of time spent in kernel networking
calls, and the amount of context switching.



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