From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: Multiple MSI, take 3 Date: Fri, 11 Jul 2008 03:32:42 -0700 (PDT) Message-ID: <20080711.033242.58168774.davem@davemloft.net> References: <20080711005719.GO14894@parisc-linux.org> <20080711102326.GR14894@parisc-linux.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:50841 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753180AbYGKKcn (ORCPT ); Fri, 11 Jul 2008 06:32:43 -0400 In-Reply-To: <20080711102326.GR14894@parisc-linux.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: matthew@wil.cx Cc: ebiederm@xmission.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, grundler@parisc-linux.org, mingo@elte.hu, tglx@linutronix.de, jgarzik@pobox.com, linux-ide@vger.kernel.org, suresh.b.siddha@intel.com, benh@kernel.crashing.org, jbarnes@virtuousgeek.org, rdunlap@xenotime.net, mtk.manpages@gmail.com From: Matthew Wilcox Date: Fri, 11 Jul 2008 04:23:26 -0600 > On Fri, Jul 11, 2008 at 03:06:33AM -0700, Eric W. Biederman wrote: > > So unless the performance of the AHCI is better by a huge amount I don't > > see the point, and even then I am extremely sceptical. > > I don't have performance numbers yet, but surely you can see that > avoiding a register read in the interrupt path is a large win? Such overhead is going to be amortized. AHCI is not like networking where we have lots of very small transactions to deal with, and therefore the per-IRQ overhead can begin to dominate. Therefore, like Eric, I think workng on multiple MSI is a very dubious usage of one's time. But, it's your time, so use it how you wish :)