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From "Pavel Yaskevich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4718) More-efficient ExecutorService for improved throughput
Date Wed, 14 May 2014 00:53:19 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13997128#comment-13997128
] 

Pavel Yaskevich commented on CASSANDRA-4718:
--------------------------------------------

The graphs Ryan posted in his previous comment (especially bdplab tests) look pretty close
to what I would expect without running the tests and just looking as 4718-sep code. The more
latency is introduced to the tasks the less effect would spinning have or in other words there
is need to spin is eliminated, because the more time execution takes the more luckily it is
that next task is already there waiting in the queue which makes thread parking/unparking
no longer a dominant factor in latencies. So I would be very interested to see even longer
running tests (especially reads) because that is much closer to the real behavior dominated
by network/disk latencies. 

> 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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