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https://issues.apache.org/jira/browse/GEODE-9365?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17417759#comment-17417759
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ASF subversion and git services commented on GEODE-9365:
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Commit 6dbd2199bab67c44fc1b34165709a5d498c7227d in geode's branch
refs/heads/develop from mhansonp
[ https://gitbox.apache.org/repos/asf?p=geode.git;h=6dbd219 ]
GEODE-9365: Removing unnecessary synchronization (#6858)
add use of atomics to close the gaps.
this addresses a possible performance problem.
> HARegionQueue over throttles when multiple threads attempt concurrent adds
> --------------------------------------------------------------------------
>
> Key: GEODE-9365
> URL: https://issues.apache.org/jira/browse/GEODE-9365
> Project: Geode
> Issue Type: Bug
> Components: client queues
> Reporter: Darrel Schneider
> Assignee: Mark Hanson
> Priority: Major
> Labels: GeodeOperationAPI, pull-request-available
>
> HARegionQueue.checkQueueSizeConstraint has some code that implements a
> "throttle" on adds to a queue that is full. It is supposed to wait
> "eventEnqueueWaitTime" before doing an add. But because this code does two
> syncs (putGuard and permitMon) and only waits on one of them, it holds the
> other sync for the duration of this threads throttle. Any other concurrent
> thread trying to add to the queue gets stuck on the putGuard sync that is
> held by the first thread that is doing the timed wait. So it ends up waiting
> "eventEnqueueWaitTime" to acquire the first sync and then ends up waiting
> again "eventEnqueueWaitTime" when it does its own timed wait. If you have 10
> concurrent threads trying to add one of them will end up waiting 10 *
> "eventEnqueueWaitTime".
> A couple ideas of how to fix this. Get rid of the putGuard and just use
> permitMon. Then as soon as the first thread goes into its timed wait another
> thread is allowed to sync on permitMon. But if this is done then we need to
> think carefully about the code inside this sync block since it can not be
> executed while one or more other threads are waiting in permitMon.
> The other solution would be to compute the elapsed time it took to get into
> the first sync and subtract that from the time we wait on permitMon. This
> seems like a simple solution but does introduce at least one call of get time
> (the second call is only needed if the queue is full).
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