Messages in this thread | | | Date | Mon, 26 May 2003 14:34:24 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [BK PATCHES] add ata scsi driver |
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On Mon, 26 May 2003, Jens Axboe wrote: > > > Think of all the fairness issues we've had in the elevator code, and > > realize that the low-level disk probably implements _none_ of those > > fairness algorithms. > > I think it does, to some extent at least.
I doubt they do a very good job of it. I know of bad cases, even with "high-end" hardware. Sure, we can hope that it's getting better, but do we want to bet on it.
> > Hmm.. Where does it keep track of request latency for requests that have > > been removed from the queue? > > Well, it doesn't...
Yeah. Which means that right now _really_ long starvation will show up as timeouts, while other cases will just show up as bad latency.
Which will _work_, of course (assuming the timeout handling is correct, which is a big if in itself), but it still sucks from a usability standpoint.
Even if we drop our timeouts from 30 seconds (or whatever they are now) down to just a few seconds, that's a _loooong_ time, and we should be a lot more proactive about things. Audio/video stuff tends to want things with latencies in the tenth-of-a-second range, even when they buffer things up internally to hide the worst cases.
Linus
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