Messages in this thread | | | Date | Fri, 19 Mar 1999 18:15:35 +0100 (CET) | From | Henrik Olsen <> | Subject | Re: disk head scheduling |
| |
On Fri, 19 Mar 1999, Mark H. Wood wrote: > 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? Since all modern harddiscs lie faster than a politician in an election year when asked about their geometry, the very idea of knowing enough about the track boundaries to switch sort direction within each track is absurd.
-- Henrik Olsen, Dawn Solutions I/S URL=http://www.iaeste.dk/~henrik/ Get the rest there.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |