[jbosscache-dev] Optimize use of CacheLoader.exists() with passivation

[Manik Surtani]

On 24 Nov 2008, at 17:45, Brian Stansberry wrote:

> I've been profiling JBoss AS web session replication, and one of the  
> significant hits I'm seeing is from calls to File.exists() from  
> FileCacheLoader (see attached).  In turn, those calls are due calls  
> from LegacyActivationInterceptor, particularly the  
> removeNodeFromCacheLoader() method, which is called with every  
> invocation.[1]  Many of these calls are on the most critical path[2]  
> so speeding them can have large implications for overall cluster  
> performance.
>
> I'm wondering if we can be smarter here and avoid most calls to  
> removeNodeFromCacheLoader()?
>
> Is it a correct statement that, logically, with passivation the only  
> time it would make sense to remove a node from the cache loader is  
> if that invocation loaded data from the cache loader?  The node  
> remove is allowed because the in-memory data has become complete;  
> the only way previously incomplete data can become complete is if a  
> request has loaded data.  So, if we can pass back to the activation  
> interceptor info on whether a load has occurred (e.g. via a simple  
> boolean flag in InvocationContext), we can avoid most calls to  
> CacheLoader.exists().
>
> Thoughts?

Makes sense.  See

https://jira.jboss.org/jira/browse/JBCACHE-1446

>
>
> [1] ActivationInterceptor would have the same problem if I were  
> using MVCC.
> [2] Up calls from JGroups. NAKACK only allows one such call per peer  
> at a time, and FC blocks web request threads based on the handling  
> of these calls, so the speed of these calls is the most critical  
> path in the whole system.
>
> -- 
> Brian Stansberry
> Lead, AS Clustering
> JBoss, a division of Red Hat
> brian.stansberry at redhat.com
> < 
> websessreplhotspots 
> .png>_______________________________________________
> jbosscache-dev mailing list
> jbosscache-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/jbosscache-dev