From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262366AbTEZXbi (ORCPT ); Mon, 26 May 2003 19:31:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262358AbTEZXbi (ORCPT ); Mon, 26 May 2003 19:31:38 -0400 Received: from pizda.ninka.net ([216.101.162.242]:53390 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id S262366AbTEZXbe (ORCPT ); Mon, 26 May 2003 19:31:34 -0400 Date: Mon, 26 May 2003 16:43:00 -0700 (PDT) Message-Id: <20030526.164300.88501443.davem@redhat.com> To: andrea@suse.de Cc: akpm@digeo.com, davidsen@tmr.com, haveblue@us.ibm.com, habanero@us.ibm.com, mbligh@aracnet.com, linux-kernel@vger.kernel.org Subject: Re: userspace irq balancer From: "David S. Miller" In-Reply-To: <20030526233446.GZ3767@dualathlon.random> References: <20030526222406.GU3767@dualathlon.random> <20030526162616.6ceacaba.akpm@digeo.com> <20030526233446.GZ3767@dualathlon.random> X-FalunGong: Information control. X-Mailer: Mew version 2.1 on Emacs 21.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Andrea Arcangeli Date: Tue, 27 May 2003 01:34:46 +0200 On Mon, May 26, 2003 at 04:26:16PM -0700, Andrew Morton wrote: > How hard would it be to make this HT-aware? yeah! that was the obvious next step. So what is idle defined as? How are you going to measure things like softirq load? How much weight will softirq load get compared to hardirq load? How will process load be factored into this and what weight will this get? All of these questions have no answer as far as the kernel is concerned, because this is a policy decision and something the user ought to be able to configure to suite his needs. All you've said today is that IRQ balancing needs to be more like the cpufreq drivers. The hardware programming and some of the delicate time sensitive details are done in the kernel, but deciding how and when to do these things belongs as some userspace action. I still contend that Arjan's usermode irq balancer solves one realm of those problems. And there is nothing that prevents his work from being extended to upload policies for the things you have brought up today. Finally, claiming this is a performance issue is moot. We've already shown that if the current IRQ load balancer in 2.5.x improves performance for any network based things there is no reasonable reason WHY this is the case bacause it's behavior is anti-networking in nature in that it thinks hardware IRQ load equates to real load which it does not.