Messages in this thread | | | Date | Mon, 10 Feb 2003 22:53:27 +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:
>Andrea Arcangeli <andrea@suse.de> wrote: > >>It's the readahead in my tree that allows the reads to use the max scsi >>command size. It has nothing to do with the max scsi command size >>itself. >> > >Oh bah. > >- *max_ra++ = vm_max_readahead; >+ *max_ra = ((128*4) >> (PAGE_SHIFT - 10)) - 1; > > >Well of course that will get bigger bonnie numbers, for exactly the reasons >I've explained. It will seek between files after every 512k rather than >after every 128k. > Though Andrea did say it is a "single threaded" streaming read. 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.
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