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https://issues.apache.org/jira/browse/AMQ-5486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15046777#comment-15046777
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Gary Tully commented on AMQ-5486:
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that looks like a sensible enhancement. my only comment would be the current
MAX_INT default appears to be being replaced with 10, as the default value
when the property is referenced. I guess it would be best to retain the current
defaults.
> Thread synchronization overhead is unexpectedly high
> ----------------------------------------------------
>
> Key: AMQ-5486
> URL: https://issues.apache.org/jira/browse/AMQ-5486
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker
> Affects Versions: 5.9.1
> Environment: UbuntuServer 12.04 x86_64, Linux Kernel 3.20.23, OpenJDK
> 1.7.0_51 64-Bit Server VM, Xms 2G, Xms 8G, CPU: E5-2620 v2 X 2, 64 GB RAM
> Reporter: Benjamin Huang
> Fix For: NEEDS_REVIEW
>
> Attachments: Method_Statistics.html, Monitor_History.zip,
> Monitor_Usage_Statistics.html, monitor_usage_stats.png,
> nio_worker_blocked_1.png, nio_worker_blocked_2.png,
> nio_worker_blocked_frequently.png, tunable_threadpool_options.patch
>
>
> There's about 20 topics with virtual topic enabled, hundreds of
> comsumers/producers connected to MQ on NIO transport connector. During the
> run there're about 12000 msg flow in per second, not a very high rate, but
> ActiveMQ consumes a lot of CPU resource (about 600%~1000%). To find out
> what's the most CPU consuming code path, I use JProfiler to dig into the
> process.
> Among all the NIO worker threads, most of them were frequently blocked and
> did a little job between the 'unblocked' time. While they're expected spend
> most of their time slices on waiting for work item and processed them.
> !nio_worker_blocked_frequently.png!
> After reviewing the monitor usage history and stats, I think these NIO
> workers were competing fiercely with each other on executing a synchronized
> method (DestinationMap::get), which is also the most hot spot in the program
> . I also notice that the caller AbstractRegion::getDestinations acquires a
> read lock before calling it, so I guess this could be a left out, read lock
> is the actual lock type required here.
> !monitor_usage_stats.png!
> !nio_worker_blocked_1.png!
> !nio_worker_blocked_2.png!
> It's too difficult for me to list all critical sections between NIO workers,
> or between NIO workers and BrokerService which adds up to the overall
> synchronize overhead. So I attach the relevant info, with the hope of finding
> a complete solution to this.
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