[aphexairlines]

There are no benchmarks showing JVM-based programs using less memory than most any other roughly equivalent programs on different runtimes. The JVM's reputation as a pig also comes from people's personal experiences -- even a simple email proxy (davmail) is easily at 100mb resident, over 1gb virtual.

[bballant]

My main point is that the JVM manages memory better than ruby. Its dead easy to benchmark it yourself by writing a pair of tiny programs. As I said, the JVM will use up all the memory it can. You can probably tweak davmail's runtime flags to use less. There is typically a CPU tradeoff if you cut back on the memory a program can use, and usually a happy middle-ground.

In my personal experience, I've re-written a few ruby utils in Java for an order of magnitude speed improvement. I've seen a ruby site crater under load because of memory issues that its java replacement easily manages (which is sorta what the OP is about). The JVM is especially well suited for handling "stateless" http requests because it's ability to quickly create and destroy small objects.