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https://issues.apache.org/jira/browse/QPID-5910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14070204#comment-14070204
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ASF subversion and git services commented on QPID-5910:
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Commit 1612559 from [~mgoulish] in branch 'qpid/trunk'
[ https://svn.apache.org/r1612559 ]
QPID-5910
The previous way of computing required credit was apparently
pretty slow -- perhaps because it is doing some unnceessary
copying down in its guts. (Which theory I did not prove.)
And it was running while a lock was held, which caused a
significant throughput regression (which was reported as an
enormous latency regression.)
The simpler means of calculating credit in this diff removes
most of the problem.
> Throughput regression relative to 0.14
> --------------------------------------
>
> Key: QPID-5910
> URL: https://issues.apache.org/jira/browse/QPID-5910
> Project: Qpid
> Issue Type: Bug
> Affects Versions: 0.22
> Reporter: michael goulish
> Assignee: michael goulish
> Fix For: 0.29
>
>
> If you use qpid-latency-test, hold message size constant, and gradually
> increase the sending rate (in several tests) you will sooner or later reach a
> point at which the messaging system's ability to handle throughput saturates.
> When that happens, latency will go sky-high. (I have producer flow-control
> turned off to be able to compare vs. older code.)
> The latest code reaches throughput saturation significantly earlier than
> older code. (i.e. at a lower sending rate.)
> Also, using 'perf' to help analyze the code, recent code is executing
> significantly fewer instructions per second than older code.
> This probably indicates that come parts of the code are spending too much
> time *while a lock is held* -- thus preventing other threads from fulfilling
> their destiny, and having an effect on overall throughput.
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