From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762608AbXKTTSP (ORCPT ); Tue, 20 Nov 2007 14:18:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754606AbXKTTSA (ORCPT ); Tue, 20 Nov 2007 14:18:00 -0500 Received: from cantor2.suse.de ([195.135.220.15]:38917 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752557AbXKTTSA (ORCPT ); Tue, 20 Nov 2007 14:18:00 -0500 To: Nick Piggin Cc: Mark Lord , Andrew Morton , Linus Torvalds , Ingo Molnar , Linux Kernel Subject: Re: CONFIG_IRQBALANCE for 64-bit x86 ? From: Andi Kleen References: <47425EA5.7000607@rtr.ca> <200711201517.16171.nickpiggin@yahoo.com.au> Date: Tue, 20 Nov 2007 20:17:57 +0100 In-Reply-To: <200711201517.16171.nickpiggin@yahoo.com.au> (Nick Piggin's message of "Tue\, 20 Nov 2007 15\:17\:15 +1100") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nick Piggin writes: > > For that matter, I'd like to know why it has been decided that the > best place for IRQ balancing is in userspace. There is a lot of possible policy in it > It should be in kernel > IMO, and it would probably allow better power saving, performance, > fairness, etc. if it were to be integrated with the task balancer as > well. Integrating with the task balancer makes really only sense if the device supports MSI-X and if it does that you don't really need an irq balancer because you can just send to all CPUs as needed. Without MSI-X you would be trying to reprogram the interrupts all the time when a task is migrating and it is highly doubtful that doing that automatically would do any good. -Andi