From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263350AbVGOR7H (ORCPT ); Fri, 15 Jul 2005 13:59:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263353AbVGOR7H (ORCPT ); Fri, 15 Jul 2005 13:59:07 -0400 Received: from ns1.suse.de ([195.135.220.2]:15262 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S263350AbVGOR5C (ORCPT ); Fri, 15 Jul 2005 13:57:02 -0400 Date: Fri, 15 Jul 2005 19:57:01 +0200 From: Andi Kleen To: Venkatesh Pallipadi Cc: Andi Kleen , "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 Message-ID: <20050715175700.GE15783@wotan.suse.de> References: <20050715102349.A15791@unix-os.sc.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050715102349.A15791@unix-os.sc.intel.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > I wouldn't say it is totally impossible. There are ways in which Linux can work > without a reliable Local APIC timer. One option being - make one CPU that gets > the external timer interrupt multicast an IPI to all the other CPUs that > wants to get periodic timer interrupt. That doesn't mix very well with variable ticks. And I believe we really need them. For no tick in idle you need a timer for each CPU that can be programmed to a reasonably long interval to wake you up after longer idleness. And all that should work without bouncing cache lines around all the time because that doesn't work on larger systems. -Andi