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Date: Mon, 01 Oct 2007 22:27:52 GMT From: Hubert Tonneau <hubert.tonneau@...lpliant.org> To: linux-kernel@...r.kernel.org Subject: Re: Network slowdown due to CFS Ingo Molnar wrote: > > Really, i have never seen a _single_ mainstream app where the use of > sched_yield() was the right choice. Pliant 'FastSem' semaphore implementation (as oppsed to 'Sem') uses 'yield' http://old.fullpliant.org/ Basically, if the ressource you are protecting with the semaphore will be held for a significant time, then a full semaphore might be better, but if the ressource will be held just a fiew cycles, then light aquiering might bring best result because the most significant cost is in aquiering/releasing. So the aquiering algorithm for fast semaphores might be: try to aquire with a hardware atomic read and set instruction, then if it fails, call yield then retry (at least on a single processor single core system). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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