Messages in this thread | | | Date | Mon, 16 Nov 1998 09:41:40 -0500 (EST) | From | Mark Hahn <> | Subject | Re: elevator algorithm bug in ll_rw_blk.c |
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> With that kind of knowledge, what kind of improvements could be made to > the driver?
actually, it's the true geometry that a disk scheduler wants, along with a model for how long a given seek will take. hdparm gives neither: the geometry is false, because all non-ancient disks are zoned, and it doesn't mention seeking (which is a nonlinear function in any case), or head-switching time.
fortunately, none of this matters much, since seeking is still basically monotonic with distance in _blocks_. this is why the current request sorting (even before the fix) can easily deliver maximal bandwidth. it basically only errs when you generate a new request at a lower absolute address (thus deferred by the sort), that in truth is in the current track, and would be very fast to fetch. that's a fairly obscure pattern...
regards, mark hahn.
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