Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965418AbXA3HjR (ORCPT ); Tue, 30 Jan 2007 02:39:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965423AbXA3HjR (ORCPT ); Tue, 30 Jan 2007 02:39:17 -0500 Received: from srv5.dvmed.net ([207.36.208.214]:43791 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965418AbXA3HjQ (ORCPT ); Tue, 30 Jan 2007 02:39:16 -0500 Message-ID: <45BEF61F.7000400@garzik.org> Date: Tue, 30 Jan 2007 02:39:11 -0500 From: Jeff Garzik User-Agent: Thunderbird 1.5.0.9 (X11/20061219) MIME-Version: 1.0 To: Ingo Molnar CC: Linus Torvalds , Stephen Hemminger , Thomas Gleixner , Linux Kernel Mailing List Subject: Re: Linux 2.6.20-rc6 - sky2 resume breakage References: <1170101430.29240.34.camel@localhost.localdomain> <20070129133849.1b523226@freekitty> <1170109401.29240.49.camel@localhost.localdomain> <20070129144055.151cfe52@freekitty> <20070129154518.40b0b3d3@freekitty> <20070129161626.33277eb1@freekitty> <20070130065457.GA23390@elte.hu> In-Reply-To: <20070130065457.GA23390@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.3 (----) X-Spam-Report: SpamAssassin version 3.1.7 on srv5.dvmed.net summary: Content analysis details: (-4.3 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1672 Lines: 37 Ingo Molnar wrote: > i'm wondering, could we go with Thomas' temporary patch that disables > sky2 MSI if CONFIG_PM is enabled - we could revert that after 2.6.20. > It's not like MSI is a life and death feature. On IO-APIC systems > vectors are abundant and in any case we share irqs just fine. The true > advantage of MSI is minimal. (MSI-X has the potential to be better by > being message based, but in reality it still goes through the full IRQ > layer.) MSI might be useful on really, really large systems - but i > really hope those really large systems dont rely on CONFIG_PM. Meanwhile > Thomas' patch maximizes the amount of working hardware (it has the > chance to produce working systems in 100% of the cases) - which is a few > orders of magnitude more important than IRQ management micro-costs. Am i > missing anything? Sharing irqs /sucks/. I routinely have to fight a USB device dying, because the ATA device is causing an interrupt storm, or vice versa. /Very/ common headache. Other than that, they use a tiny bit fewer CPU cycles, and allow simplification of the interrupt handler (saving another few CPU cycles). The biggest benefit is (a) for hardware designers, where MSI means a cleaner h/w design, and (b) preparation of drivers and the kernel systems for MSI-only hardware. At present only high end hardware is MSI-only (like infiniband), but that's the future direction. Jeff - 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/