Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754496AbYGKKMc (ORCPT ); Fri, 11 Jul 2008 06:12:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751698AbYGKKMX (ORCPT ); Fri, 11 Jul 2008 06:12:23 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:50058 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751435AbYGKKMW (ORCPT ); Fri, 11 Jul 2008 06:12:22 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Matthew Wilcox Cc: 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 References: <20080711005719.GO14894@parisc-linux.org> Date: Fri, 11 Jul 2008 03:06:33 -0700 In-Reply-To: <20080711005719.GO14894@parisc-linux.org> (Matthew Wilcox's message of "Thu, 10 Jul 2008 18:57:19 -0600") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-SA-Exim-Connect-IP: 24.130.11.59 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa04 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Matthew Wilcox X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0002] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa04 1397; Body=1 Fuz1=1 Fuz2=1] * 0.4 FVGT_m_MULTI_ODD Contains multiple odd letter combinations * 0.0 XM_SPF_Neutral SPF-Neutral Subject: Re: Multiple MSI, take 3 X-SA-Exim-Version: 4.2 (built Thu, 03 Mar 2005 10:44:12 +0100) X-SA-Exim-Scanned: Yes (on mgr1.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1257 Lines: 31 Matthew Wilcox writes: > I'd like to thank Michael Ellerman for his feedback. This is a much > better patchset than it used to be. There is a reason we don't have an API to support this. Linux can not reasonably support this, especially not on current X86. The designers of the of the AHCI were idiots and should have used MSI-X. Attempting to support multiple irqs in an MSI capability breaks every interesting use of an irq. mask/unmask is will likely break because the mask bit is optional and when it is not present we disable the msi capability. We can not set the affinity individually so we can not allow different queues to be processed on different cores. So in general it seems something that we have to jump through a million hurdles and the result is someones twisted parody of a multiple working irqs, that even Intel's IOMMU can't cure. 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. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/