Messages in this thread | | | Date | Fri, 19 Mar 1999 10:41:31 -0800 (PST) | From | David Lang <> | Subject | Re: disk head scheduling |
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On Fri, 19 Mar 1999, Mark H. Wood wrote:
> Date: Fri, 19 Mar 1999 07:04:45 -0500 (EST) > From: Mark H. Wood <mwood@IUPUI.Edu> > To: unlisted-recipients: ; > Cc: linux-kernel@vger.rutgers.edu > Subject: Re: disk head scheduling > > On Fri, 19 Mar 1999, Ingo Molnar wrote: > > On Thu, 18 Mar 1999, Yasushi Saito wrote: > > > What I tried to implement was two-way elevator seeking (SCAN). In my > > > tiny benchmark that let many threads write on random files, SCAN > > > showed a throughput improvement of anywhere between 0 to 20%. But I > > > also noticed benefits in the original algorithm (it's fairer), so I > > > don't know if my change makes sense. > > > > the bigger problem is that dumber devices will just execute non-forwards > > ordered requests. Most modern harddisks will either cache a full track, or > > will reorder the request per-track anyway, but eg. a floppy disk or a > > CD-ROM will execute the requests as given, and the 'downwards' queue will > > perform badly. Would you mind doing the seek benchmark on your CDROM too, > > just to test this theory? > > Well of course a 2-way elevator should sort by *ascending* sector within > descending track. I take it this is difficult? > > --
Many (most? all new?) IDE drives lie to you about the real heads/sectors of the drive so you do not have the ability to do this accuratly.
David Lang
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