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https://issues.apache.org/jira/browse/VELOCITY-606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12615604#action_12615604
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Malcolm Edgar commented on VELOCITY-606:
----------------------------------------

Very interesting, always keen to see how we can improve Velocities performance.

With regard to the alternative classes, I believe supporting JDK .14 is still 
very important in Velocity so I would be keen to use alternative 1.4 compatible 
implementations:

EDU.oswego.cs.dl.util.concurrent.ConcurrentReaderHashMap

and

org.apache.commons.lang.text.StrBuilder

regards Malcolm Edgar




> Velocity 1.5 performance bottlenecks
> ------------------------------------
>
>                 Key: VELOCITY-606
>                 URL: https://issues.apache.org/jira/browse/VELOCITY-606
>             Project: Velocity
>          Issue Type: Bug
>          Components: Engine
>    Affects Versions: 1.5
>         Environment: Win XP, 1 Gb, single core, Maven 2, JUnitPerf, JRat, 
> cached Velocity templates with a ClassLoader
>            Reporter: Jarkko Viinamäki
>         Attachments: velocity-1.5-250-threads-loadtest.PNG, 
> velocity-1.5-50-threads-loadtest.PNG
>
>
> I did some quite extensive profiling to identify performance bottlenecks in 
> Velocity 1.5.
> Using Maven 2, JUnitPerf and JRat I was able to identify these methods as top 
> bottlenecks:
> org.apache.velocity.util.introspection        ClassMap - 
> findMethod(String,Object[])
> org.apache.velocity.util.introspection        IntrospectorBase - 
> getMethod(Class,String,Object[])
> org.apache.velocity.runtime.parser.node       SimpleNode - literal()
> org.apache.velocity.runtime.parser.node       SimpleNode - 
> render(InternalContextAdapter,Writer)
> org.apache.commons.collections        ExtendedProperties - 
> getBoolean(String,boolean)
> org.apache.velocity.runtime.parser.node       ASTReference - 
> render(InternalContextAdapter,Writer)
> The first two eat over 50% of the CPU with many threads. See attached 
> screenshots.
> Interestingly enough the synchronized
> org.apache.velocity.runtime   RuntimeInstance getTemplate(String,String)
> isn't a big problem when templates are cached. However, if all resources are 
> not cached it becomes a serious performance bottleneck. ResourceCacheImpl 
> also uses a synchronized map which slows things down.
> I think these bottlenecks could be at least made less worse by reducing 
> synchronization by using ConcurrentHashMap and StringBuilder that ship with 
> JDK 1.5. I'm investigating what kind of benefits could be achieved with those.

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