Re: An elevator algorithm

From: Peter Osterlund (peter.osterlund@mailbox.swipnet.se)
Date: Tue Sep 19 2000 - 16:09:47 EST

Jens Axboe <axboe@suse.de> writes:

> > modification Peter suggested there can be more and we should track the one
> > more on the back of the queue. I don't think it's worthwhile.
>
> Agree, I don't think the added complexity would be worth it.

So that leaves two choices:

1. Perfect elevator (CSCAN) without the O(1) optimization. (My second
   patch.)
2. Suboptimal elevator with the O(1) optimization. (Andrea's suggested
   modification to my second patch.)

Since the request queue can not be very long, minimizing disk head
movements ought to be more important than saving a few CPU cycles, so
I vote for the first alternative. 

-- 
Peter Österlund          Email:     peter.osterlund@mailbox.swipnet.se
Sköndalsvägen 35                    f90-pos@nada.kth.se
S-128 66 Sköndal         Home page: http://home1.swipnet.se/~w-15919
Sweden                   Phone:     +46 8 942647

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