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From "Carsten Ziegeler (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FELIX-4638) Event Admin - Less locking on event handler timing
Date Fri, 19 Sep 2014 06:30:34 GMT

    [ https://issues.apache.org/jira/browse/FELIX-4638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14140080#comment-14140080

Carsten Ziegeler commented on FELIX-4638:

Thanks for your patch, Bob - I think it definitely makes sense to reduce the locking and also
use the JMX timings.
The second patch looks good to me for handlers that use blacklisting - however :) if a handler
is configured to be ignored for blacklisting, in the previous version now thread from the
thread pool was used to execute it and the overhead was close to zero (no locking/syncing
at all). While with your patch in place, the same code is now executed regardless whether
blacklisting is used or not. It would be great if we can get the best of both solutions :)

> 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
>            Priority: Minor
>             Fix For: eventadmin-1.4.4
>         Attachments: FELIX-4638.patch, FELIX-4638b.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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