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From "Sree Panchajanyam D (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AMQ-2629) What the relationship is among "CursorMemoryUsage" and "QueueSize"
Date Tue, 23 Aug 2011 11:28:29 GMT

    [ https://issues.apache.org/jira/browse/AMQ-2629?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13089398#comment-13089398
] 

Sree Panchajanyam D commented on AMQ-2629:
------------------------------------------

Non-persistent messages are stored in memory before they are sent to consumers. CursoryMemoryUsage
indicates the memory(heap) used by non-persistent messages. This is usually capped at 70%
of heap space. This is configuration is made in activemq.xml. When the cursory memory usage
goes beyond the capped value( say 70% by default) the incoming messages are written to tempstore(
a location on disk) and all the messages from memory are flushed to tempstore, here the CursorMemoryUsage
becomes 0%. When you hit tempstore the dequeueing and enqueueing slows down because of disk
writes. 

When queue size increases CursorMemoryUsage increases till a capped value and then becomes
zero . After this enqueue and dequeue operations slow down due to disk writes involved.

> What the relationship is among "CursorMemoryUsage" and "QueueSize"
> ------------------------------------------------------------------
>
>                 Key: AMQ-2629
>                 URL: https://issues.apache.org/jira/browse/AMQ-2629
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Message Store
>    Affects Versions: 5.2.0
>         Environment: Windows2003 server - JDK 1.5.0_09-b03
>            Reporter: SPES G200
>             Fix For: 5.2.0
>
>
> Hi to everybody,  
>   
> In my application, that has 2 fast producers and 1 slow consumer, after some hours of
job, where "Queue Size" various among 0 and 1000, "CursorMemoryUsage" it begins to increase
him. This phenomenon provokes a deceleration both of "Enqueue" that "Dequeue", and even if
they are stopped the producers the speed of "dequeue" it doesn't increase. When "Queue Size"
returns to 0, "CursorMemoryUsage" it doesn't decrease.  
>   
> When this phenomenon happens I have seen that also her "Heap Memory Usage" it grows.
 
>   
> Do you have some explanation to this phenomenon?  
> What the relationship is among "CursorMemoryUsage" and "QueueSize."  
>   
> Thanks in advance 

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