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https://issues.apache.org/jira/browse/QPID-8385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17002893#comment-17002893
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Alex Rudyy commented on QPID-8385:
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I spent more time investigating the reported issue and updated JIRA description
based on my investigation results. It seems, that the main contributor for
performance degradation on dequeueing of queue entries from ring overflow
policy handler is a high CPU consumption caused by setting
{{DelayedAcquisitionStateListeners}} on the same queue entry from multiple IO
threads. Based on publishers performance, there could be thousand of
{{DelayedAcquisitionStateListeners}} created and set on the head queue entry.
The ring overflow policy should track the last dequeueing entry in order to
avoid dequeueing of the same entry from multiple concurrent threads (possibly
similar to consumer {{QueueContext#_lastSeenEntry}}).
The next message to dequeue should be evaluated based on last seen entry
rather than looking into head of the queue entry list. Only after introducing
of queue entry tracking into ring policy handler we can have a look into
further optimisation of dequeue operation with using
{{AsyncAutoCommitTransaction}} instead of {{AutoCommitTransaction}}.
> [Broker-J] Improve performance of dequeuing old queue entries on triggering
> ring policy
> ---------------------------------------------------------------------------------------
>
> Key: QPID-8385
> URL: https://issues.apache.org/jira/browse/QPID-8385
> Project: Qpid
> Issue Type: Improvement
> Components: Broker-J
> Reporter: Alex Rudyy
> Priority: Major
> Fix For: qpid-java-broker-8.0.0
>
> Attachments:
> 0001-QPID-8385-Broker-J-Delete-queue-entry-asynchronously.patch,
> 0001-QPID-8385-Broker-J-Utilize-AsyncAutoCommitTransactio.patch
>
>
> The performance of dequeuing old queue entries with triggering ring policy is
> affected by the following factors:
> * the oldest entry is not deleted immediately. As result, the deletion of
> the same oldest entry can be requested from multiple publishing IO threads
> * only one publishing thread can acquire the message with
> {{QueueEntry#acquireOrSteal}}, whilst the rest of publishing IO threads would
> set a {{DelayedAcquisitionStateListener}}. As result, thousands of
> {{DelayedAcquisitionStateListeners}} can be potentially set on the same queue
> entry
> * Setting of {{DelayedAcquisitionStateListeners}} from concurrent IO threads
> can consume host CPU up to 100% as there is a tight loop in
> {{StateChangeListenerEntry#add(StateChangeListenerEntry<T,E>)}}. There is a
> risk of running into defect {{QPID-8393}} whilst setting a listener.
> * The old message is deleted in IO thread blocking the enqueing of new
> messages
> It seems that high CPU consumption on setting of
> {{DelayedAcquisitionStateListeners}} is the main contributor for the
> perfromance degradation on old entries dequeueing by ring policy.
> The current approach for dequeuing of old queue entries from ring policy
> should be revisited. We need a mechanism to avoid multiple dequeueing of the
> same queue entry from concurrent threads. Only after introduction of such
> mechanism we can look into further performance optimisation for deletion of
> persistent queue entries.
> AutoCommitTransaction is used to dequeue entries on message expiration or
> breaching ring policy threshold. As result, the dequeueing operation for
> persistent queue entry blocks until queue entry record is removed from the
> store and the underlying store transaction is synced to disk. The sequential
> removal of multiple entries can results in unnecessary delays due to syncing
> disk on every dequeue.
> The broker performance for the corner cases described above can be
> significantly improved by using asynchronous transactions in dequeue
> operations.
> Asynchronous transaction does not wait for the store dequeue transaction to
> sync to disk. As result, the performance of removal unneeded queue entries
> can increase.
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