From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [patch for playing] 2.5.65 patch to support > 256 disks Date: Tue, 25 Mar 2003 23:12:55 +1100 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <3E8047C7.4070009@cyberone.com.au> References: <200303211056.04060.pbadari@us.ibm.com> <3E7C4251.4010406@torque.net> <20030322030419.1451f00b.akpm@digeo.com> <3E7C4D05.2030500@torque.net> <20030322040550.0b8baeec.akpm@digeo.com> <20030325105629.GS2371@suse.de> <3E803FDF.1070401@cyberone.com.au> <20030325120121.GV2371@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20030325120121.GV2371@suse.de> List-Id: linux-scsi@vger.kernel.org To: Jens Axboe Cc: Andrew Morton , dougg@torque.net, pbadari@us.ibm.com, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org 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. > > >>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!