From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261730AbVGNVhI (ORCPT ); Thu, 14 Jul 2005 17:37:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261732AbVGNVhH (ORCPT ); Thu, 14 Jul 2005 17:37:07 -0400 Received: from fmr14.intel.com ([192.55.52.68]:34734 "EHLO fmsfmr002.fm.intel.com") by vger.kernel.org with ESMTP id S261730AbVGNVhE convert rfc822-to-8bit (ORCPT ); Thu, 14 Jul 2005 17:37:04 -0400 X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 8BIT Subject: RE: [PATCH] i386: Selectable Frequency of the Timer Interrupt Date: Thu, 14 Jul 2005 17:35:33 -0400 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PATCH] i386: Selectable Frequency of the Timer Interrupt Thread-Index: AcWIWmDchQJij/LWQViSUIBmjHKYUAAYKwdA From: "Brown, Len" To: "Maciej W. Rozycki" , "Lee Revell" Cc: "dean gaudet" , "Chris Wedgwood" , "Andrew Morton" , , , , , , , , , , , X-OriginalArrivalTime: 14 Jul 2005 21:35:35.0691 (UTC) FILETIME=[F85B1DB0:01C588BB] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org >Of course using APIC internal timers is generally the best idea on SMP, >but they may have had reasons to avoid them (it's not an ISA interrupt, so >it could have been simply out of question in the initial design). Best? No. Local APIC timers are based on a clock which on many processors will STOP when the processor enters power saving idle states, such as C3. So the LAPIC timer will not accurately reflect how much time has passed across entry/exit from idle. True, this has not been an issue on SMP, since there have not been SMP systems shipping with C3, but as you know soon everything interesting will be SMP... -Len