From mboxrd@z Thu Jan 1 00:00:00 1970 From: Doug Ledford Subject: Re: [PATCH 2.5.17] Making SCSI not copy the request structure Date: Wed, 22 May 2002 18:53:49 -0400 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20020522185349.D2819@redhat.com> References: <200205212311.g4LNBYo09061@localhost.localdomain> <20020522154406.A17222@eng2.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20020522154406.A17222@eng2.beaverton.ibm.com>; from patmans@us.ibm.com on Wed, May 22, 2002 at 03:44:06PM -0700 List-Id: linux-scsi@vger.kernel.org To: Patrick Mansfield Cc: James Bottomley , linux-scsi@vger.kernel.org On Wed, May 22, 2002 at 03:44:06PM -0700, Patrick Mansfield wrote: > Do you think the queue depth on some of the adapters/devices should be > shrunk or the request queue increased with your patch? Some adapters set Actually, more appropriate for future versions would be to make the queue depth adjustable. Justin's aic driver sets the depth to 253 because he can't increase it later if he wants to, but he can queue things up internally if he ever needs to decrease it. If low level drivers had some way of signalling up the stack "hey, this is how many queue slots I can handle on this particular device now" at their leisure, then that would be a far superior option to what we have now which is the mid layer saying to the low level drivers "OK, tell me how many commands you can support on this list of devices and you have to stick with that until the next reboot". So, instead of the mid layer calling into the low level driver to tell it to set queue depths, I think the low level driver should be allowed to call into the mid layer and have the mid layer adjust the queue depth on a device. This should, of course, be properly locked so that a low level driver can change it's mind about a device's queue depth later if it wishes and call back into the mid layer with a new queue depth value without confusing the mid layer. -- Doug Ledford 919-754-3700 x44233 Red Hat, Inc. 1801 Varsity Dr. Raleigh, NC 27606