Messages in this thread | | | Date | Fri, 19 Jan 2001 02:40:23 +0100 | From | Jens Axboe <> | Subject | Re: 2.4.1pre8 slowdown on dbench tests |
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On Fri, Jan 19 2001, Andrea Arcangeli wrote: > On Thu, Jan 18, 2001 at 03:17:13PM -0200, Marcelo Tosatti wrote: > > Jens, can be the -blk patch the reason for the slowdown I'm seeing? > > This heuristic is way too aggressive: > > /* > * Try to keep 128MB max hysteris. If not possible, > * use half of RAM > */ > high_queued_sectors = (total_ram * 2) / 3; > low_queued_sectors = high_queued_sectors - MB(128); > if (low_queued_sectors < 0) > low_queued_sectors = total_ram / 2; > > /* > * for big RAM machines (>= 384MB), use more for I/O > */ > if (total_ram >= MB(384)) { > high_queued_sectors = (total_ram * 4) / 5; > low_queued_sectors = high_queued_sectors - MB(128); > } > > 2/3 of ram locked down in the I/O queue is way too much. 1/3 should be > ok. big RAM machines needs way less than 1/3 locked down.
Yes I agree, that values should probably be tweaked a bit. I'll try and squeeze some testing in to generate the best possible values.
-- * Jens Axboe <axboe@suse.de> * SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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