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https://issues.apache.org/jira/browse/CASSANDRA-4718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13986032#comment-13986032
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Jason Brown commented on CASSANDRA-4718:
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bq. The Semaphore is blocking
After reading the correct jdk source class this time, I was mistaken about the
blocking (i.e. park) aspect of Semaphore (got caught up in the rest of
AbstractQueuedSynchronizer, which Semaphore subclasses and uses internally).
Thus, I'll test out your branch as is this afternoon.
bq. It isn't forked - this is all in the same extension class that you
introduced
I didn't consider this a 'fork' as we're not mucking about with the internals
of the FJP itself.
bq. FJP uses an exclusive lock for enqueueing work onto the pool, but does more
whilst owning the lock, so is likely to take longer within the critical section
Perhaps, but the overall improvement in performance (should we attribute that
to the work stealing?) seems compelling enough.
> 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: Jason Brown
> Priority: Minor
> Labels: performance
> Fix For: 2.1.0
>
> Attachments: 4718-v1.patch, PerThreadQueue.java, baq vs trunk.png, 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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