From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Date: Tue, 15 Jul 2008 22:37:51 +0000 Subject: Re: [SUGGESTION]: drop virtual merge accounting in I/O requests Message-Id: <20080715.153751.71531968.davem@davemloft.net> List-Id: References: <20080714.183116.121978835.davem@davemloft.net> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: mpatocka@redhat.com Cc: andi@firstfloor.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, jens.axboe@oracle.com From: Mikulas Patocka Date: Tue, 15 Jul 2008 18:32:37 -0400 (EDT) > On Mon, 14 Jul 2008, David Miller wrote: > > > From: Mikulas Patocka > > Date: Mon, 14 Jul 2008 19:16:17 -0400 (EDT) > > > > > So the question is: to reduce number of requests by 12% on an outdated > > > SCSI card, it is sensible to maintain complicated merge accounting logic > > > in the core block layer? To me, it doesn't seem sensible. > > > > Rip out the code if you like, then. I really don't have time to > > work on this myself. So if you do, by all means do whatever > > you think is appropriate. > > So add signed-off line and forward it to Linus. > > Signed-off-by: Mikulas Patocka I said remove code, not turn if off. I guess you didn't like that option even though you seem heavily convinced that it buys us essentially nothing, and I'm even starting to agree with you. If the VMERGE code is going to stay, and it's a bug or a limitation in the sparc64 IOMMU code, I'd rather that get fixed. I have FUJITA's excellent analysis of the sparc64 specific IOMMU issue in my inbox and I intend to have a look at it when I get a chance. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762846AbYGOWiE (ORCPT ); Tue, 15 Jul 2008 18:38:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754087AbYGOWhw (ORCPT ); Tue, 15 Jul 2008 18:37:52 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:40573 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751661AbYGOWhv (ORCPT ); Tue, 15 Jul 2008 18:37:51 -0400 Date: Tue, 15 Jul 2008 15:37:51 -0700 (PDT) Message-Id: <20080715.153751.71531968.davem@davemloft.net> To: mpatocka@redhat.com Cc: andi@firstfloor.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, jens.axboe@oracle.com Subject: Re: [SUGGESTION]: drop virtual merge accounting in I/O requests From: David Miller In-Reply-To: References: <20080714.183116.121978835.davem@davemloft.net> X-Mailer: Mew version 5.2 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mikulas Patocka Date: Tue, 15 Jul 2008 18:32:37 -0400 (EDT) > On Mon, 14 Jul 2008, David Miller wrote: > > > From: Mikulas Patocka > > Date: Mon, 14 Jul 2008 19:16:17 -0400 (EDT) > > > > > So the question is: to reduce number of requests by 12% on an outdated > > > SCSI card, it is sensible to maintain complicated merge accounting logic > > > in the core block layer? To me, it doesn't seem sensible. > > > > Rip out the code if you like, then. I really don't have time to > > work on this myself. So if you do, by all means do whatever > > you think is appropriate. > > So add signed-off line and forward it to Linus. > > Signed-off-by: Mikulas Patocka I said remove code, not turn if off. I guess you didn't like that option even though you seem heavily convinced that it buys us essentially nothing, and I'm even starting to agree with you. If the VMERGE code is going to stay, and it's a bug or a limitation in the sparc64 IOMMU code, I'd rather that get fixed. I have FUJITA's excellent analysis of the sparc64 specific IOMMU issue in my inbox and I intend to have a look at it when I get a chance.