From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261602AbVGRKrJ (ORCPT ); Mon, 18 Jul 2005 06:47:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261551AbVGRKrJ (ORCPT ); Mon, 18 Jul 2005 06:47:09 -0400 Received: from pollux.ds.pg.gda.pl ([153.19.208.7]:40712 "EHLO pollux.ds.pg.gda.pl") by vger.kernel.org with ESMTP id S261602AbVGRKrH (ORCPT ); Mon, 18 Jul 2005 06:47:07 -0400 Date: Mon, 18 Jul 2005 11:47:07 +0100 (BST) From: "Maciej W. Rozycki" To: Andi Kleen Cc: Venkatesh Pallipadi , "Brown, Len" , akpm@osdl.org, linux-kernel@vger.kernel.org, torvalds@osdl.org, vojtech@suse.cz, christoph@lameter.com Subject: Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt In-Reply-To: <20050715175819.GF15783@wotan.suse.de> Message-ID: References: <20050715102349.A15791@unix-os.sc.intel.com> <20050715175819.GF15783@wotan.suse.de> 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 On Fri, 15 Jul 2005, Andi Kleen wrote: > > That's like scratching your left ear with your right hand -- broadcasting > > that external timer interrupt in the first place is more straightforward. > > If you want to exclude CPUs from the list of receivers, just use the > > logical destination mode appropriately. > > The problem with that is that it would need regular synchronizations > of all CPUs to coordinate this. Not good for scalability and I > believe the fundamentally wrong way to do this. What to you mean by "regular synchronizations of all CPUs?" And how is a broadcasted external timer interrupt different from a unicasted one redistributed further via an all-but-self IPI, except from removing an unnecessary burden from the CPU targeted by the unicast interrupt? Maciej