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From "Carsten Ziegeler (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (FELIX-4638) Event Admin - Less locking on event handler timing
Date Mon, 29 Sep 2014 07:58:33 GMT

     [ https://issues.apache.org/jira/browse/FELIX-4638?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Carsten Ziegeler resolved FELIX-4638.
    Resolution: Fixed

Thanks for the updated patch, Bob. I think this is a good step in the right direction to achieve
less locking and have minimum overhead. Therefore I have applied the patch. I think we can
track additional improvements/changes in new issues.
I also think it would be great to have different perf test cases (small set of handlers, many
handlers and some of them configured to be ignored etc.), this could give is a better overview
of how things improve or might get worse for other scenarios.

> Event Admin - Less locking on event handler timing
> --------------------------------------------------
>                 Key: FELIX-4638
>                 URL: https://issues.apache.org/jira/browse/FELIX-4638
>             Project: Felix
>          Issue Type: Improvement
>          Components: Event Admin
>            Reporter: Bob Paulin
>            Assignee: Carsten Ziegeler
>            Priority: Minor
>             Fix For: eventadmin-1.4.4
>         Attachments: FELIX-4638.patch, FELIX-4638b.patch, FELIX-4638c.patch
> The locking that is done for the blacklist timing seems to degrade performance significantly
Felix is under stress with multiple firing handler callbacks for each event.  I'd like to
discuss an alternative approach with less locking that still  guarantees proper event ordering
per the OSGi spec.  Basically instead of using the CyclicBarriers (Rendezvous) on a per handler
basis we could use a count down latch to only await after all handlers are complete.  Then
instead of using a stopwatch based timer the JMX Current Thread Cpu Time which counts CPU
time for the application code and any IO performed on it's behalf filtering out time context
switching between threads to provide proper blacklisting.  
> Here are my test results.
> Baseline(Event Admin 1.4.2):
> 15 Threads
> 100000 Async Events per Thread
> 7 Active Handlers per Event
> For a total of 10500000 Handler Events Executed in 40000 - 45000ms
> With the same parameters above but a CountDownLatch I see the execution time drop to
around 25000ms.   The improvement is noticeable because the stress test includes 7 active
handlers per event.  The improvement is less noticeable with applications that only register
one or 2 handlers for an active event such as in the PerformanceTestIT.  Thoughts on changing
how this locking occurs?  Concerns with using the JMX timings?

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