[jboss-jira] [JBoss JIRA] (JASSIST-163) RuntimeSupport.find2Methods a perf hotspot when proxy's methods are called at higher concurrency

[Nikita Tovstoles (JIRA)]

    [ https://issues.jboss.org/browse/JASSIST-163?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12725707#comment-12725707 ] 

Nikita Tovstoles commented on JASSIST-163:
------------------------------------------

Hi, Brett & Scott:

I contributed [the fix above|https://issues.jboss.org/browse/JASSIST-163?focusedCommentId=12681065&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-12681065] (ie "eager initialization") awhile ago. This patch throws out lazy init altogether as I wanted to avoid synchronization and did not think lazy initialization would buy any memory savings at steady state as:
* most - if not all - ORM apps, in my view, end up using all mapped entities over the course of the app (thus eventually same amount of heap is allocated in both eager and lazy scenarios)
* even if some initialized properties are never used, the extra memory consumption is too insignificant - a string per domain class property - to warrant added code complexity (and potential lock contention) of 

FWIW our web API, integrated into [sites with significant traffic|http://ecorebates.com/our-clients/], has been running on this patch for 6+ months without any issues. YMMV ;-

                
> RuntimeSupport.find2Methods a perf hotspot when proxy's methods are called at higher concurrency
> ------------------------------------------------------------------------------------------------
>
>                 Key: JASSIST-163
>                 URL: https://issues.jboss.org/browse/JASSIST-163
>             Project: Javassist
>          Issue Type: Enhancement
>    Affects Versions: 3.15.0-GA, 3.16.1-GA
>         Environment: hibernate-core 3.6.10.Final
>            Reporter: Nikita Tovstoles
>            Assignee: Shigeru Chiba
>             Fix For: 3.17.0-GA
>
>         Attachments: blocked-threads.png, find2methods-hotspot.png, jassist-163-fix.patch, monitor-backtraces.png, monitor-backtraces.png, Product.java, Product_$$_javassist_0-post-patch.java, Product_$$_javassist_0.java, Tomcat-2012-03-28(2).zip
>
>
> We've been profiling our Hibernate 3.6.10-based app and noticed a perf bottleneck in javassist.util.proxy.RuntimeSupport.find2methods. Unfortunately, this method, which has a synch. block, is being called on
> every invocation of every proxied entity method (see javassist.util.proxy.ProxyFactory.makeForwarder(), called indirectly by
> ProxyFactory.createClass()).
> In our testing, the result is that our service call's latency increases from 33 to 55, 260, 400ms as concurrency increases
> 1-10-20-30 users on a 4-core CPU. At 20 and 30 users 51% of CPU time is spent contending for a monitor in RuntimeSupport.find2methods:
> {code}
>         synchronized (methods) {
>             if (methods[index] == null) {
>                 methods[index + 1] = thisMethod == null ? null
>                                      : findMethod(self, thisMethod, desc);
>                 methods[index] = findSuperMethod(self, superMethod, desc);
>             }
>         }
> {code} 
> Since find2methods merely interrogates class metadata, seems like its return values should be cached (in a ConcurrentMap?) instead of repeatedly executing the above synchronized statement. Instead, currently, it's being called every time (?) a proxied method is executed - see *Invocation Count* in this screen shot:
> https://issues.jboss.org/secure/attachment/12353025/monitor-backtraces.png
> Full [YourKit profile|http://yourkit.com] is [attached as a ZIP archive|^Tomcat-2012-03-28(2).zip]; key screen shots from the snapshot also attached separately

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