[jira] Updated: (VELOCITY-223) VMs that use a large number of directives and macros use excessive amounts of memory - over 4-6MB RAM per form

["Ryan Smith (JIRA)" <de...@velocity.apache.org>]

     [ https://issues.apache.org/jira/browse/VELOCITY-223?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ryan Smith updated VELOCITY-223:
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    Attachment: VelocityMemory.JPG

This is a picture of the YourKit memory for all of the owned objects for one of our library files.

> VMs that use a large number of directives and macros use excessive amounts of memory - over 4-6MB RAM per form
> --------------------------------------------------------------------------------------------------------------
>
>                 Key: VELOCITY-223
>                 URL: https://issues.apache.org/jira/browse/VELOCITY-223
>             Project: Velocity
>          Issue Type: Bug
>          Components: Engine
>    Affects Versions: 1.3.1
>         Environment: Operating System: All
> Platform: All
>            Reporter: Christian Nichols
>             Fix For: 1.6
>
>         Attachments: VelocityMemory.JPG
>
>
> Our application FinanceCenter is based on Velocity as the template engine.  We 
> have a library of about 200 macros and about 400 VM files.  Because the 
> velocity parser copies the macro body into the VM during parsing, macros that 
> are frequently used (even though identical and using local contexts) use up 
> large amounts of memory.  On our Linux server (running Redhat 7.2 with Sun JDK 
> 1.4.1_04) we can easily use up over 1GB of RAM simply by opening up many forms 
> (about 150) - the server starts out using 60MB after startup.  This memory 
> times out after 5 minutes and is returned which tells me that it is screen 
> memory.  Our problem is that the NT JVM and Linux JVM (32 bit) are currently 
> limited to about 1.6 - 2.0 GB of ram for heap space.  Thus, using a fair number 
> of forms in the application leaves little space for user session data.
> We have implemented a caching mechanism for compiled templates and integrated 
> it into Velocity so that cached objects are timed out of the cache but the 
> server is still using large amounts of memory.  We finally had to rewrite many 
> of our macros into Java so that memory usage would be reduced (note that these 
> macros were doing complex screen formatting not business logic).  Doing this 
> has reduced our memory by about 30%.  This is currently our biggest issue with 
> Velocity and is causing us to review our decision to stay with Velocity going 
> forward.  This is because we will likely end up with close to 1,000 forms by 
> the end of next year and need to know that Velocity can deal with this.  Is 
> there any work underway to share compiled macro AST's?  This would greatly 
> reduce the amount of memory used.  I have reviewed the parser code that is 
> doing this but it seems that this is an embedded part of the design and not 
> easily changed.

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