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https://issues.apache.org/jira/browse/CASSANDRA-21285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18071304#comment-18071304
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C. Scott Andreas edited comment on CASSANDRA-21285 at 4/5/26 9:01 PM:
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Uploaded jfr-comparison.zip which includes a JFR capture from trunk and with
this patch applied as of 1f5c87c in my fork.
Measurement methodology for attached captures: build project, launch instance
via CCM, launch 5-minute test of linked workload above, perform JFR capture
during test.
Specifically:
{{– ant realclean jar && ccm create && ccm populate -n 1 && ccm start; sleep
10;}}
{{– }}{{bin/cassandra-easy-stress run GrowingPartitions --partitions 1000
--duration 5m --readrate 0.8 --rate 5000}}
{{export PID=$(ps ax | grep CassandraDaemon | cut d ' ' -f 1 | head -n 1);
}}{{– }}{{echo "Profiling $PID..."; jcmd $PID JFR.start name=profile
settings=profile +jdk.ObjectAllocationInNewTLAB#enabled=true
+jdk.ObjectAllocationOutsideTLAB#enabled=true
+jdk.ObjectAllocationSample#enabled=true duration=300s
filename=/tmp/cassandra-profile$PID.jfr; sleep 300; open
/tmp/cassandra-profile-$PID.jfr}}
was (Author: cscotta):
Uploaded jfr-comparison.zip which includes a JFR capture from trunk and with
this patch applied as of 1f5c87c in my fork.
Measurement methodology for attached captures: build project, launch instance
via CCM, launch 5-minute test of linked workload above, perform JFR capture
during test.
Specifically:
– `ant realclean jar && ccm create && ccm populate -n 1 && ccm start; sleep 10;`
– `bin/cassandra-easy-stress run GrowingPartitions --partitions 1000 --duration
5m --readrate 0.8 --rate 5000`
– `export PID=$(ps ax | grep CassandraDaemon | cut -d ' ' -f 1 | head -n 1);
echo "Profiling $PID..."; jcmd $PID JFR.start name=profile settings=profile
+jdk.ObjectAllocationInNewTLAB#enabled=true
+jdk.ObjectAllocationOutsideTLAB#enabled=true
+jdk.ObjectAllocationSample#enabled=true duration=300s
filename=/tmp/cassandra-profile-$PID.jfr; sleep 300; open
/tmp/cassandra-profile-$PID.jfr`
> 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
> Assignee: C. Scott Andreas
> Priority: Low
> Fix For: 6.x
>
> Attachments: CASSANDRA-21285.diff, after.png, before.png,
> buffer-false.allocs.txt, buffer-false.png, initial-patch.allocs.txt,
> initial-patch.png, jfr-comparison.zip
>
>
> 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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