Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756495AbZCDOxH (ORCPT ); Wed, 4 Mar 2009 09:53:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753091AbZCDOwx (ORCPT ); Wed, 4 Mar 2009 09:52:53 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:43248 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752853AbZCDOww (ORCPT ); Wed, 4 Mar 2009 09:52:52 -0500 To: Matthew Wilcox Cc: linux-pci@vger.kernel.org, jbarnes@virtuousgeek.org, linux-kernel@vger.kernel.org References: <1235410082-5016-1-git-send-email-matthew@wil.cx> From: ebiederm@xmission.com (Eric W. Biederman) Date: Wed, 04 Mar 2009 06:52:39 -0800 In-Reply-To: <1235410082-5016-1-git-send-email-matthew@wil.cx> (Matthew Wilcox's message of "Mon\, 23 Feb 2009 12\:27\:56 -0500") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in01.mta.xmission.com;;;ip=67.169.126.145;;;frm=ebiederm@xmission.com;;;spf=neutral X-SA-Exim-Connect-IP: 67.169.126.145 X-SA-Exim-Rcpt-To: matthew@wil.cx, linux-kernel@vger.kernel.org, jbarnes@virtuousgeek.org, linux-pci@vger.kernel.org X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa01 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: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 XM_SPF_Neutral SPF-Neutral Subject: Re: Support for multiple MSI X-SA-Exim-Version: 4.2.1 (built Thu, 25 Oct 2007 00:26:12 +0000) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1537 Lines: 35 Matthew Wilcox writes: > Currently, Linux supports multiple MSI-X interrupts per device, but only > a single MSI interrupt. This patch series adds support to the generic > PCI code for supporting multiple MSI interrupts. Architectures will > need to add support for multiple MSIs, and I have a patch to do that for > x86 (which needs some more work). Getting this patch series in first > is important so we can start supporting this interface in drivers and > architectures independently. Do we have any benchmarks anywhere that show that multiple msi support gains us something? The requirement to allocate a contiguous block of vector numbers worries me for the x86 implementation. I don't like the idea of having to deal with allocations that can fail because of fragmentation. The fact that we also can not honor the irq affinity properly for multiple msi also disturbs me. At a quick skim your patchset is only the generic code without a single architecture specific implementation so it appears you have not done the hard work on figuring out how to deal with multiple msi in the real world. Given that msi-x does not have any of these issues without data to say that there is a true gain in supporting multi-msi I don't see the point of supporting it. 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/