Messages in this thread | | | Date | Mon, 10 Feb 2003 13:28:56 +0100 | From | Andrea Arcangeli <> | Subject | Re: stochastic fair queueing in the elevator [Re: [BENCHMARK] 2.4.20-ck3 / aa / rmap with contest] |
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On Mon, Feb 10, 2003 at 11:17:30PM +1100, Nick Piggin wrote: > Andrea Arcangeli wrote: > > >On Mon, Feb 10, 2003 at 03:48:08AM -0800, 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. > >> > > > >NOTE: first there is no seek at all in the benchmark we're talking > >about, no idea why you think there are seeks. This is not tiobench, this > >is bonnie sequential read. > > > Yes, Andrew obviously missed this... Anyway, could it be due to > a big stripe size and hitting more disks in the RAID? How does > a single SCSI disk perform here, Andrea?
Actually I increased readahead to more than just 512k in my last tree, especially to take care of RAID :) so that both lowlevel will get the 512k, instead of being limited to 256k command each 8) This might apply to hardware raid too.
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