From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262239AbTE0BSb (ORCPT ); Mon, 26 May 2003 21:18:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262528AbTE0BQD (ORCPT ); Mon, 26 May 2003 21:16:03 -0400 Received: from ppp-217-133-42-200.cust-adsl.tiscali.it ([217.133.42.200]:23250 "EHLO dualathlon.random") by vger.kernel.org with ESMTP id S262430AbTE0BPE (ORCPT ); Mon, 26 May 2003 21:15:04 -0400 Date: Tue, 27 May 2003 03:28:18 +0200 From: Andrea Arcangeli To: Dave Jones , "David S. Miller" , 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 Message-ID: <20030527012818.GI3767@dualathlon.random> References: <20030527000639.GA3767@dualathlon.random> <20030526.171527.35691510.davem@redhat.com> <20030527004115.GD3767@dualathlon.random> <20030526.174841.116378513.davem@redhat.com> <20030527010903.GF3767@dualathlon.random> <20030527011620.GB7135@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030527011620.GB7135@suse.de> User-Agent: Mutt/1.4i X-GPG-Key: 1024D/68B9CB43 X-PGP-Key: 1024R/CB4660B9 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 27, 2003 at 02:16:20AM +0100, Dave Jones wrote: > On Tue, May 27, 2003 at 03:09:03AM +0200, Andrea Arcangeli wrote: > > > > So I'm asking you, again, how are you going to measure softirq load in > > > making hardware IRQ load balancing decisions? Watching the scheduling > > > > rdtsc could do it very well, irqs and softirqs can't be rescheduled so > > you can tick measure how long you take in each cpu > > On CPUs that vary frequency, this will break, unless TSC scales > with frequency. You cannot assume that this will be the case. those stats would per-second or similar anyways. so unless you change frequency every second it won't matter. it's an heuristic. And especially if you change frequency on all cpus at nearly the same time as I expect it will matter even less since it would decrease the window even more. Andrea