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https://issues.apache.org/jira/browse/CASSANDRA-9558?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14598451#comment-14598451
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Olivier Michallat commented on CASSANDRA-9558:
----------------------------------------------
Coalescing is handled by
[Connection.Flusher|https://github.com/datastax/java-driver/blob/2.0/driver-core/src/main/java/com/datastax/driver/core/Connection.java#L825]
in the driver, it's scheduled on the event loop.
Based on Benedict's feedback, I'm experimenting with [these
changes|https://github.com/datastax/java-driver/commit/9ab18c454f67175904af98377454ba60e7fa9958]
to avoid artificially delaying message, but I'm not observing a significant
difference yet, at least in the context of cassandra-stress tests.
> Cassandra-stress regression in 2.2
> ----------------------------------
>
> Key: CASSANDRA-9558
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9558
> Project: Cassandra
> Issue Type: Bug
> Reporter: Alan Boudreault
> Assignee: T Jake Luciani
> Fix For: 2.2.x
>
> Attachments: 2.1.log, 2.2.log, CASSANDRA-9558-2.patch,
> CASSANDRA-9558-ProtocolV2.patch, atolber-CASSANDRA-9558-stress.tgz,
> atolber-trunk-driver-coalescing-disabled.txt,
> stress-2.1-java-driver-2.0.9.2.log, stress-2.1-java-driver-2.2+PATCH.log,
> stress-2.1-java-driver-2.2.log, stress-2.2-java-driver-2.2+PATCH.log,
> stress-2.2-java-driver-2.2.log
>
>
> We are seeing some regression in performance when using cassandra-stress 2.2.
> You can see the difference at this url:
> http://riptano.github.io/cassandra_performance/graph_v5/graph.html?stats=stress_regression.json&metric=op_rate&operation=1_write&smoothing=1&show_aggregates=true&xmin=0&xmax=108.57&ymin=0&ymax=168147.1
> The cassandra version of the cluster doesn't seem to have any impact.
> //cc [~tjake] [~benedict]
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