Date: Thu, 29 Mar 2001 13:19:05 -0800 From: Fabio Riccardi <fabio@chromium.com> To: linux-kernel@vger.kernel.org Subject: linux scheduler limitations? Hello, I'm working on an enhanced version of Apache and I'm hitting my head against something I don't understand. I've found a (to me) unexplicable system behaviour when the number of Apache forked instances goes somewhere beyond 1050, the machine suddently slows down almost top a halt and becomes totally unresponsive, until I stop the test (SpecWeb). Profiling the kernel shows that the scheduler and the interrupt handler are taking most of the CPU time. I understand that there must be a limit to the number of processes that the scheduler can efficiently handle, but I would expect some sort of gradual performance degradation when increasing the number of tasks, instead I observe that by increasing Apache's MaxClient linit by as little as 10 can cause a sudden transition between smooth working with lots (30-40%) of CPU idle to a total lock-up. Moreover the max number of processes is not even constant. If I increase the server load gradually then I manage to have 1500 processes running with no problem, but if the transition is sharp (the SpecWeb case) than I end-up having a lock up. Anybody seen this before? Any clues? - Fabio - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/