From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261423AbVFMRJ4 (ORCPT ); Mon, 13 Jun 2005 13:09:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261814AbVFMRJ4 (ORCPT ); Mon, 13 Jun 2005 13:09:56 -0400 Received: from e34.co.us.ibm.com ([32.97.110.132]:64174 "EHLO e34.co.us.ibm.com") by vger.kernel.org with ESMTP id S261423AbVFMRJ1 (ORCPT ); Mon, 13 Jun 2005 13:09:27 -0400 Date: Mon, 13 Jun 2005 22:39:41 +0530 From: Srivatsa Vaddagiri To: Tony Lindgren Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] Dynamic tick for x86 version 050609-2 Message-ID: <20050613170941.GA1043@in.ibm.com> Reply-To: vatsa@in.ibm.com References: <88056F38E9E48644A0F562A38C64FB6004EBD10C@scsmsx403.amr.corp.intel.com> <20050609014033.GA30827@atomide.com> <20050610043018.GE18103@atomide.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050610043018.GE18103@atomide.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi Tony, I went through the dynamic-tick patch on your website (patch-dynamic-tick-2.6.12-rc6-050610-1) and was having some questions about it: 1. dyn_tick->skip is set to the number of ticks that have to be skipped. This is set on the CPU which is the last (in online_map) to go idle and is based on when that CPU's next timer is set to expire. Other CPUs also seem to use the same interval to skip ticks. Shouldnt other CPU check their nearest timer rather than blindly skipping dyn_tick->skip number of ticks? 2. reprogram_apic_timer seems to reprogram the count-down APIC timer (APIC_TMICT) with an integral number of apic_timer_val. How accurate will this be? Shouldnt this take into account that we may not be reprogramming the timer on exactly "jiffy" boundary? 3. Is there any strong reason why you reprogram timers only when _all_ CPUs are idle? 4. In what aspects you think does your patch differ from VST (other than not relying on HRT!)? -- Thanks and Regards, Srivatsa Vaddagiri, Linux Technology Center, IBM Software Labs, Bangalore, INDIA - 560017