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On Sun, 5 Jun 2005, Ingo Molnar wrote: > > * Esben Nielsen <simlo@phys.au.dk> wrote: > > > When K is a constant or bounded by a constant (140 in this > > application) any function which is O(K) is O(1) per definition of O! > > technically you are right. But the question is - while K is considered a > constant, and N (nr_running_RT_tasks) is technically not bounded - in > practice N is bounded just as much. Have you ever seen any hard-RT > application that has more than 140 threads _running at the same time_ on > a single CPU? You can even enforce it to be theoretically bounded, via > ulimits. > > in fact, K and N should be pretty close to each other for most > applications. I'd be interested in real application scenarios where N is > much (== more than 10 times) larger than K and plists really matter. > I think that would only be the case when an application has an error. The problem now is: Say you have two RT applications running, one living in priority 0-49 and one in 50-99. Let us say the second has such an error, like keep spawning threads whichs blocks on a mutex owned by a task which is blocked forever. Without plists such an error will kill the high priority RT task. With plists it will only see a _limited_ effect on it's latency. You can say plists is better at isolating applications wrt. timing than ordinary sorted lists. > Ingo > - 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/ | ||||||||||||
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