Messages in this thread | | | From | Hubert Tonneau <> | Subject | Re: Network slowdown due to CFS | Date | Mon, 01 Oct 2007 22:27:52 GMT |
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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).
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