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https://issues.apache.org/jira/browse/CASSANDRA-21285?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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C. Scott Andreas updated CASSANDRA-21285:
-----------------------------------------
Description:
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]
was:
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]
> 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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