From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: Re: Degraded I/O performance, since 2.5.41 Date: Thu, 10 Oct 2002 16:48:47 -0700 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <3DA611DF.3000206@us.ibm.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from westrelay05.boulder.ibm.com (westrelay05.boulder.ibm.com [9.17.193.33]) by e32.co.us.ibm.com (8.12.2/8.12.2) with ESMTP id g9ANmrpw058232 for ; Thu, 10 Oct 2002 19:48:53 -0400 Received: from nighthawk.sr71.net (dyn9-47-17-248.beaverton.ibm.com [9.47.17.248]) by westrelay05.boulder.ibm.com (8.12.3/NCO/VER6.4) with ESMTP id g9ANnD4K118730 for ; Thu, 10 Oct 2002 17:49:13 -0600 Received: from us.ibm.com (nighthawk [127.0.0.1]) by nighthawk.sr71.net (8.11.6/8.11.6) with ESMTP id g9ANmlU00939 for ; Thu, 10 Oct 2002 16:48:47 -0700 List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org Linus Torvalds wrote: > In article <3DA4D34F.3070106@us.ibm.com> you write: > >>When I run a certain large webserver benchmark, I prefer to warm the >>pagecache up with the file set first, to cheat a little :) I grep >>through 20 different 500MB file sets in parallel to do this. It is >>a _lot_ slower in the BK snapshot than in plain 2.5.41. > > Can you pinpont where this started happening? There aren't that many > changes since 2.5.41 that I'd consider suspicious, and it would help > to try to pinpoint it a bit. Using stupid brute force, I narrowed it down to 12 patches. The only one that touches generic SCSI code is the queue length one. 1.704.1.2, in my tree from dledford@redhat.com. Backing it out fixed my problem. CC'ing him... I would guess that it's just making stupid, er.... suboptimal, decisions about the length for my hardware. With a controller as "smart" as the ServeRAID, I would imagine the best approach is to just throw as many requests at it at one time as you can, then let the controller sort it out. Doug, I noticed that you changed a bunch of code to the aic7xxx_old driver, is this just a lack of optimization in the ServeRAID driver? -- Dave Hansen haveblue@us.ibm.com