Messages in this thread | | | From | Con Kolivas <> | Subject | Re: [PATCH] mm: yield during swap prefetching | Date | Thu, 9 Mar 2006 13:30:13 +1100 |
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On Thu, 9 Mar 2006 01:22 pm, Nick Piggin wrote: > Pavel Machek wrote: > >On Út 07-03-06 16:05:15, Andrew Morton wrote: > >>Why do you want that? > >> > >>If prefetch is doing its job then it will save the machine from a pile of > >>major faults in the near future. The fact that the machine happens > > > >Or maybe not.... it is prefetch, it may prefetch wrongly, and you > >definitely want it doing nothing when system is loaded.... It only > >makes sense to prefetch when system is idle. > > Right. Prefetching is obviously going to have a very low work/benefit, > assuming your page reclaim is working properly, because a) it doesn't > deal with file pages, and b) it is doing work to reclaim pages that > have already been deemed to be the least important. > > What it is good for is working around our interesting VM that apparently > allows updatedb to swap everything out (although I haven't seen this > problem myself), and artificial memory hogs. By moving work to times of > low cost. No problem with the theory behind it. > > So as much as a major fault costs in terms of performance, the tiny > chance that prefetching will avoid it means even the CPU usage is > questionable. Using sched_yield() seems like a hack though.
Yeah it's a hack alright. Funny how at last I find a place where yield does exactly what I want and because we hate yield so much noone wants me to use it all.
Cheers, Con - 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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