We did some additional testing by tweaking web applications to use local interfaces to EJBs. These comparisons were made to our performance tests conducted earlier (http://www.amitysolutions.com.au/downloads/JBoss_optimizations.pdf)
We found that they had little impact over the optimizations that JBoss performs internally. We saw perhaps a 1 ms decrease in the response time average, using the IBM SDK 1.4.0 with an optimized JBoss 3.2.0. In our test applications, we built the servlets so that they obtained references to EJBs only at initialization. So that nullified the PortableRemoteObject operation disadvantage. In a production system, you don't expect the references to change so we feel it is a reasonable performance tweak. Therefore, we were only measuring the speed improvement of passing by reference. With small amounts of data transferred between EJBs and servlets on a per transaction basis, the gain is small if not negligible from our results. If you were consistently transferring large blocks of data such as BLOBs for pictures, you might see more substantial performance gains. Images appeared to display faster when we inspected some pages incorporating BLOB derived pictures, although we would need to measure this to obtain a proper understanding of the gain. >From a memory perspective, we saw a 4Mb reduction in the virtual size (VSZ) and a 1.5Mb reduction in the resident in memory footprint (RSS) using the IBM SDK 1.4.0 with an optimized JBoss 3.2.0. Hope that is of use.
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