Messages in this thread | | | Date | Tue, 25 Mar 2003 13:35:02 +0100 | From | Jens Axboe <> | Subject | Re: [patch for playing] 2.5.65 patch to support > 256 disks |
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On Tue, Mar 25 2003, Nick Piggin wrote: > Jens Axboe wrote: > > >On Tue, Mar 25 2003, Nick Piggin wrote: > > > >> > >>Nice Jens. Very good in theory but I haven't looked at the > >>code too much yet. > >> > >>Would it be possible to have all queues allocate out of > >>the one global pool of free requests. This way you could > >>have a big minimum (say 128) and a big maximum > >>(say min(Mbytes, spindles). > >> > > > >Well not really, as far as I can see we _need_ a pool per queue. Imagine > >a bio handed to raid, needs to be split to 6 different queues. But our > >minimum is 4, deadlock possibility. It could probably be made to work, > >however I greatly prefer a per-queue reserve. > > > OK yeah you are right there. In light of your comment below > I'm happy with that. I was mostly worried about queues being > restricted to a small maximum.
Understandable, we'll make max tunable.
> >>This way memory usage is decoupled from the number of > >>queues, and busy spindles could make use of more > >>available free requests. > >> > >>Oh and the max value can easily be runtime tunable, right? > >> > > > >Sure. However, they don't really mean _anything_. Max is just some > >random number to prevent one queue going nuts, and could be completely > >removed if the vm works perfectly. Beyond some limit there's little > >benefit to doing that, though. But MAX could be runtime tunable. Min is > >basically just to make sure we don't kill ourselves, I don't see any > >point in making that runtime tunable. It's not really a tunable. > > > OK thats good then. I would like to see max removed, however perhaps > the VM isn't up to that yet. I'll be testing this when your code > solidifies!
Only testing will tell, so yes you are very welcome to give it a shot. Let me release a known working version first :)
-- Jens Axboe
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