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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4718) More-efficient ExecutorService for improved throughput
Date Fri, 16 May 2014 11:23:40 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13998622#comment-13998622
] 

Benedict commented on CASSANDRA-4718:
-------------------------------------

bq. (latest bdplab tests)

Which latest bdplab tests? The longer bdplab test from before (not the latest tests) had some
issues (unrelated to this ticket) so we didn't get any read results, but showed increased
write throughput.

The latest tests have all been short runs. I am actually very pleased we are _at all_ faster
for bdplab on any workload, as the first versions of these patches did not seem to benefit
older hardware/kernels (we don't have enough hardware configurations to say which was the
deciding factor), and actually incurred a slight penalty. The fact that the gap is very narrow
for bdplab is not really important, nor are the thrift numbers. In both of those instances
I am interested only in that we _do not perform any worse_; performing slightly better even
here is just a bonus.




> More-efficient ExecutorService for improved throughput
> ------------------------------------------------------
>
>                 Key: CASSANDRA-4718
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4718
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: Benedict
>            Priority: Minor
>              Labels: performance
>             Fix For: 2.1.0
>
>         Attachments: 4718-v1.patch, PerThreadQueue.java, aws.svg, aws_read.svg, backpressure-stress.out.txt,
baq vs trunk.png, belliotsmith_branches-stress.out.txt, jason_read.svg, jason_read_latency.svg,
jason_write.svg, op costs of various queues.ods, stress op rate with various queues.ods, v1-stress.out
>
>
> Currently all our execution stages dequeue tasks one at a time.  This can result in contention
between producers and consumers (although we do our best to minimize this by using LinkedBlockingQueue).
> One approach to mitigating this would be to make consumer threads do more work in "bulk"
instead of just one task per dequeue.  (Producer threads tend to be single-task oriented by
nature, so I don't see an equivalent opportunity there.)
> BlockingQueue has a drainTo(collection, int) method that would be perfect for this. 
However, no ExecutorService in the jdk supports using drainTo, nor could I google one.
> What I would like to do here is create just such a beast and wire it into (at least)
the write and read stages.  (Other possible candidates for such an optimization, such as the
CommitLog and OutboundTCPConnection, are not ExecutorService-based and will need to be one-offs.)
> AbstractExecutorService may be useful.  The implementations of ICommitLogExecutorService
may also be useful. (Despite the name these are not actual ExecutorServices, although they
share the most important properties of one.)



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