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https://issues.apache.org/jira/browse/CASSANDRA-4718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14000830#comment-14000830
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Benedict commented on CASSANDRA-4718:
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I meant 250Kop/s. We're now pushing 6Kop/s. The numbers from 16th May are the
latest posted, to my knowledge, and the ones we're discussing?
You can make stress do a fixed number of ops per run, but not a fixed set of
thread counts currently - its auto mode (that this is from) ramps up thread
counts until it detects a plateau; in these tests it seems that sep reached a
higher throughput rate earlier, and so when it normalised down again stress
considered it to have plateaued earlier. As to #2, run1 when it is truncated at
a lower tc is as fast as stock is at its peak. However, you're right that it is
possible it would have tanked further - in this case this would be indicative
of a bug rather than a fundamental flaw in its design, but it is almost
certainly down to the natural tendency to dip slightly below peak throughput
after the real plateau.
I can patch stress briefly to force it to run all thread counts in the
requested range, instead of stopping when it hits a plateau, but the auto-mode
isn't really designed to be a canonical test. If we want accurate like-for-like
comparisons we want to graph each thread count separately for its whole run,
and ensure each run is long enough to spot the general behavioural pattern
(i.e. at least a few minutes for IO bound work). I'd also ensure we interleaved
the two branches to try to avoid any weird page caching / other utilisation
interferences.
> 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,
> austin_diskbound_read.svg, 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_run1.svg, jason_run2.svg, jason_run3.svg, jason_write.svg, op costs of
> various queues.ods, stress op rate with various queues.ods,
> stress_2014May15.txt, stress_2014May16.txt, 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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