From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262775AbVGMVd6 (ORCPT ); Wed, 13 Jul 2005 17:33:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262815AbVGMVbK (ORCPT ); Wed, 13 Jul 2005 17:31:10 -0400 Received: from dvhart.com ([64.146.134.43]:58038 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S262351AbVGMV3H (ORCPT ); Wed, 13 Jul 2005 17:29:07 -0400 Date: Wed, 13 Jul 2005 14:29:02 -0700 From: "Martin J. Bligh" Reply-To: "Martin J. Bligh" To: Chris Wedgwood , Andrew Morton Cc: Lee Revell , "Brown, Len" , dtor_core@ameritech.net, torvalds@osdl.org, vojtech@suse.cz, david.lang@digitalinsight.com, davidsen@tmr.com, kernel@kolivas.org, linux-kernel@vger.kernel.org, diegocg@gmail.com, azarah@nosferatu.za.org, christoph@lameter.com Subject: Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt Message-ID: <368700000.1121290141@flay> In-Reply-To: <20050713211650.GA12127@taniwha.stupidest.org> References: <42D3E852.5060704@mvista.com> <20050712162740.GA8938@ucw.cz> <42D540C2.9060201@tmr.com> <20050713184227.GB2072@ucw.cz> <1121282025.4435.70.camel@mindpipe> <1121286258.4435.98.camel@mindpipe> <20050713134857.354e697c.akpm@osdl.org> <20050713211650.GA12127@taniwha.stupidest.org> X-Mailer: Mulberry/2.1.2 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org >> Len Brown, a year ago: "The bottom line number to laptop users is >> battery lifetime. Just today somebody complained to me that Windows >> gets twice the battery life that Linux does." > > It seems the motivation for lower HZ is really: > > (1) ACPI/SMM suckage in laptops > > (2) NUMA systems with *horrible* remote memory latencies It makes a difference on more normal SMP systems as well, just not as much. See earlier in the thread. The NUMA system I used as an example was actually a newer one with something like a 4:1 ratio, not an older one with 20:1 or so. I have a feeling it's more to do with the number of procs and the scheduler being invoked more than it is really to do with NUMA ratios. It seems people are agreed we want sub-HZ timers, and eventually go to tickless ... the question is more what to do in the meantime. M.