From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH] fixes and cleanups for the new command allocation code Date: 04 Feb 2003 19:53:57 -0600 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <1044410039.3485.61.camel@mulgrave> References: <20030204162326.A30755@lst.de> <20030204081616.A24105@beaverton.ibm.com> <20030204175146.A31515@lst.de> <20030204091955.A24785@beaverton.ibm.com> <1044383605.2014.23.camel@mulgrave> <20030204202935.A325@lst.de> <1044399797.3484.15.camel@mulgrave> <20030204172505.A28812@beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: (from root@localhost) by pogo.mtv1.steeleye.com (8.9.3/8.9.3) id RAA21224 for ; Tue, 4 Feb 2003 17:54:04 -0800 In-Reply-To: <20030204172505.A28812@beaverton.ibm.com> List-Id: linux-scsi@vger.kernel.org To: Patrick Mansfield Cc: Christoph Hellwig , SCSI Mailing List On Tue, 2003-02-04 at 19:25, Patrick Mansfield wrote: > But if we have a lot of prepped commands around we will be allocating > memory that is not (currently) needed, we could end up using an equal > number of scsi_cmnd's as we have blk requests. I would rather we not > allocate or hold onto scsi_cmnd in such cases. (And generally in all > cases, but that goes beyond.) But that's not how the block queue works: prep is actually called from elv_next_request(). Therefore, if you plug the queue in the request function when you're over the queue limit, you only get a single fully prepped request waiting in the queue, which, I think, is the desired behaviour. Even if the queue is restarted because of I/O pressure, it will begin with the prepped request and re-block. > We are still missing single_lun checking. And the slave_{alloc,configure,destroy} needs fixing too. > I would like to see the patch in a tree before 2.5.60 (probably already > too late), and then we can take care of these other issues. I think some > systems/disks will barf if they are flooded with QUEUE FULLs. OK, I concur, we can't do without throttling. I'll put it in and we can try to fix up around it. James