Messages in this thread | | | Date | Sun, 15 Nov 1998 16:02:09 -0800 | From | "Jeffrey B. Siegal" <> | Subject | Re: linux-kernel-digest V1 #2824 (was: elevator) |
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>On Fri, 13 Nov 1998, Jeffrey B. Siegal wrote: > >> I vaguely recall reading in some operating system book that >> this is modified version of the elevator algorithm >> meant increase fairness. Otherwise, the access to block 5 >> might be delayed a *long* time if lots of high-value >> blocks are requested. > >But it will never be starved. I do not have hard figures, but I'd >make an educated guess that the modification Philip proposed will >be beneficial more often than not.
That depends on how you define benefit. It will decreae the mean service time, but increase the service time variance. Is that beneficial? It depends.
Also, adding accesses to the current pass will bias accesses such those at the end of the disk will be serviced faster than those at the beginning. This is similar to the one-way vs. two-way elevator issue discussed by others.
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