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https://issues.apache.org/jira/browse/CASSANDRA-4718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13997529#comment-13997529
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Benedict commented on CASSANDRA-4718:
-------------------------------------
I've force pushed an updated branch to the repository which is simpler and has
some nicer properties (though is ~1% slower at lower thread counts). I'm pretty
happy with its current state, although still need to create some thorough
executor stress tests.
In the latest version workers self coordinate descheduling through a simpler
scheme than the separate descheduler. The new scheme also permits thread
over-provisioning to be corrected incredibly promptly (i.e. almost instantly),
eliminating my one concern about this approach (that it could be slightly
resource unfriendly in cases of variable workloads when sharing the underlying
platform with another service).
The latest version also delivers more consistency in its throughput rate by
using a ConcurrentSkipListMap to order the spinning threads in order of
expected schedule time, and by force-scheduling a new worker if a producer
encounters a full task queue when not all workers are yet scheduled.
> 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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