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https://issues.apache.org/jira/browse/AMQ-4467?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15815002#comment-15815002
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Christopher L. Shannon commented on AMQ-4467:
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Ah ok, I understand better now thanks for the explanation. So the core
behavior hasn't changed and now the usage just goes up to 100% if using
multiple destinations. Now that I think about it, I'm pretty sure I've seen
this behavior happen where dispatch slows to a crawl down when memory usage
hits the high water mark because future dispatched messages have to wait for
messages to be acked as shown in your test at 50%.
Purging the cursor is an interesting idea and I think would be a nice
improvement. Clearing out the the cursor cache if the destination is inactive
so other active destinations get access to all of the memory certainly seems
like the ideal solution. If I get some time I will play around with this a
little bit as a feature for the 5.15 release.
> Memory usage percent can be exceeded much if PFC is disabled
> ------------------------------------------------------------
>
> Key: AMQ-4467
> URL: https://issues.apache.org/jira/browse/AMQ-4467
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker
> Affects Versions: 5.x
> Reporter: SuoNayi
> Assignee: Gary Tully
> Fix For: 5.15.0
>
> Attachments: AMQ-4467.patch
>
>
> If PFC is disabled, when the store cursor checks limits, it checks only the
> memory percentage of its own MemoryUsage and compares it to the high water
> mark. Otherwise if PFC is enabled, it checks whether the MemoryUsage is
> "full" but the "isFull" method also checks its parents.
> This issue arrises when you have memory limits set on queues higher than the
> overall system limit, as well as if you have multiple queues who's memory
> limits combined are higher than the overall system limit. These settings must
> be taken into account.
> The original form can be found at
> http://activemq.2283324.n4.nabble.com/What-can-be-reason-of-460-memory-usage-limit-td4665651.html
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