[jira] [Commented] (CASSANDRA-6488) Batchlog writes consume unnecessarily large amounts of CPU on vnodes clusters

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-6488?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13848379#comment-13848379 ] 

Jonathan Ellis commented on CASSANDRA-6488:
-------------------------------------------

NB: I'm not sure what the changes to candidates/chosenEndpoints do so I've left that out for now.

> Batchlog writes consume unnecessarily large amounts of CPU on vnodes clusters
> -----------------------------------------------------------------------------
>
>                 Key: CASSANDRA-6488
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6488
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Rick Branson
>            Assignee: Aleksey Yeschenko
>         Attachments: 6488-rbranson-patch.txt, 6488-v2.txt, graph (21).png
>
>
> The cloneTokenOnlyMap call in StorageProxy.getBatchlogEndpoints causes enormous amounts of CPU to be consumed on clusters with many vnodes. I created a patch to cache this data as a workaround and deployed it to a production cluster with 15,000 tokens. CPU consumption drop to 1/5th. This highlights the overall issues with cloneOnlyTokenMap() calls on vnodes clusters. I'm including the maybe-not-the-best-quality workaround patch to use as a reference, but cloneOnlyTokenMap is a systemic issue and every place it's called should probably be investigated.



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