Messages in this thread | | | Date | Mon, 10 Feb 2003 23:27:13 +1100 | From | Nick Piggin <> | Subject | Re: stochastic fair queueing in the elevator [Re: [BENCHMARK] 2.4.20-ck3 / aa / rmap with contest] |
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Andrew Morton wrote:
>Nick Piggin <piggin@cyberone.com.au> wrote: > >>That is what I can't understand. Movement of the disk head should >>be exactly the same in either situation and 128K is not exactly >>a pitiful request size - so it suggests a quirk somewhere. It >>is not as if the disk has to be particularly smart or know a >>lot about the data in order to optimise the head movement for >>a load like this. >> > >Yes, that's a bit odd. Some reduction in CPU cost and bus >traffic, etc would be expected. Could be that sending out a >request which is larger than a track is saving a rev of the disk >for some reason. > Shouldn't be. Even at 128KB readahead we should always have outstanding requests against the disk in a streaming read scenario, right? Maybe if the track buffers are bigger than 128K?
Is there a magic number above which you see the improvement, Andrea? Or does it steadily climb?
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