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    <p>Short answer: no, I don't think this looks scary.</p> <p>I don't think you have enough information here to determine exactly where the spiky behavior comes from. There's nothing that indicates that there's a memory leak, thread leak, resource leak or obvious contention. Perhaps some of your tasks managed to get in step with each other? In any case, you seem to be observing correct behavior and nothing in the profile indicates dangerous symptoms.</p> <p>That said, I would stronly recommend that you upgrade to the latest version of Java. Update 3 is too old: we're not even allowed to use it at work due to the security issues. There has been plenty of work done on the garbage collector since then as well.</p> <p>As a first step, I would recommend upgrading to latest Java (update 20 as of this writing) and re-run your test. It's entirely possible that this puzzling behavior will vanish on the second try.</p> <p>EDIT: with respect to the instant deadlock found in the comment, I wouldn't use that finding as an indication of anything other than multithreaded programming is hard (do-able but hard). I've recommended Java Concurrency in Practice before and I strongly recommend that you keep it nearby while coding.</p> <p>That said, I would also recommend avoiding RMI if at all possible. The hard-wired coupling that creates between client and server (client hangs until server fulfills request) can cause another layer of distributed computing complexity that really isn't worth it for a simple "request + fulfill" pairing.</p> <p>Congrats on finding the deadlock, though. There are plenty of times when I wish my own (RMI-caused) issues were as straightforward....</p>
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    1. COThanks for the Java update tip, I'll do that and run the test again tonight. Tasks getting into step with each other is something I haven't really considered, the wait time is randomized but maybe I should look into that. And yes, I do share your view that this doesn't look inherently scary, since, like you said, resources don't seem to be leaking.
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    2. COI'll be damned, after a couple hours of frustration I found out that the profiler I'm using causes an almost instant deadlock in my connection pool running with Java 6 update 20, but not with update 3, at least that's what it seems like. This experiment will have to wait until this weekend.
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    3. COMy stubborness kept me going last night, I upgraded to JProfiler 6 and voila, things are running without deadlocks again. But, the escalating spike pattern persists, no change there. I'll run this on linux over the weekend, for curiosity's sake. I'll check out Java Concurrency in Practice, I've always been on somewhat of a "need to know" basis when it comes to java concurrency, understanding things just enough to make them work but really having to work for it when it comes to debugging said code :).
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