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Posted to commits@cassandra.apache.org by "C. Scott Andreas (Jira)" <ji...@apache.org> on 2026/04/05 00:35:00 UTC
[jira] [Commented] (CASSANDRA-21285) Reduce allocations + copies due to rebuffering in LocalDataResponse row serialization
[ https://issues.apache.org/jira/browse/CASSANDRA-21285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18071121#comment-18071121 ]
C. Scott Andreas commented on CASSANDRA-21285:
----------------------------------------------
Branch: [https://github.com/cscotta/cassandra/tree/CASSANDRA-21285]
> Reduce allocations + copies due to rebuffering in LocalDataResponse row serialization
> -------------------------------------------------------------------------------------
>
> Key: CASSANDRA-21285
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21285
> Project: Apache Cassandra
> Issue Type: Task
> Components: Messaging/Client
> Reporter: C. Scott Andreas
> Priority: Normal
> Attachments: CASSANDRA-21285.diff, after.png, before.png
>
>
> This patch reduces allocations due to rebuffering in LocalDataResponse row serialization.
> Today, LocalDataResponse#build serializes row responses without providing a size estimate when initializing a DataOutputBuffer. Read responses that exceed the initial size of 128 bytes incur progressive size doubling, allocation, and buffer copying until the result fits.
> This patch maintains a lightweight moving average of read response sizes and uses this to size the initial response.
> In a read-heavy workload dominated by resultset paging, this change reduces memory allocations/copies by about 9%. [1]
> The change is most visible in the Native-Transport-Requests threadpool.
> *Trunk:*
> {{Thread Pool Threads Allocated Count % of Total}}
> {{----------------------------------------------------------------------------------------------------}}
> {{Native-Transport-Requests 10 68.45 GiB 348,724 74.02%}}
> *Trunk + Patch:*
> {{Thread Pool Threads Allocated Count % of Total}}
> {{----------------------------------------------------------------------------------------------------}}
> {{Native-Transport-Requests 11 62.52 GiB 324,523 74.13%}}
> ---
> [1] Workload example: [https://gist.github.com/cscotta/580378387c73b49822f287910771d14f]
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