From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262865AbVGOAF2 (ORCPT ); Thu, 14 Jul 2005 20:05:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262821AbVGOAF1 (ORCPT ); Thu, 14 Jul 2005 20:05:27 -0400 Received: from zproxy.gmail.com ([64.233.162.193]:52894 "EHLO zproxy.gmail.com") by vger.kernel.org with ESMTP id S262872AbVGOAEu convert rfc822-to-8bit (ORCPT ); Thu, 14 Jul 2005 20:04:50 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=r8sa/klHxcyiqS2BBRGO20fS0Uzk7QBy+CkZXFttYQr3LRnK0nRFgXplzfOinLG9uB5p4rn0HORMtqbo7lJeYQN0gVQ3oldXp8Fnp0sxgB769v5SGIPUF5vKZoJmmbUXk/DgZkpIDmTJZxGf+QB5veNvE0VRCjSNEf7Wcwvc3y8= Message-ID: <9a874849050714170465c979c3@mail.gmail.com> Date: Fri, 15 Jul 2005 02:04:50 +0200 From: Jesper Juhl Reply-To: Jesper Juhl To: Chris Wedgwood Subject: Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt Cc: Andrew Morton , 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, mbligh@mbligh.org, diegocg@gmail.com, azarah@nosferatu.za.org, christoph@lameter.com In-Reply-To: <20050713211650.GA12127@taniwha.stupidest.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Content-Disposition: inline References: <42D3E852.5060704@mvista.com> <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> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 7/13/05, Chris Wedgwood wrote: > On Wed, Jul 13, 2005 at 01:48:57PM -0700, Andrew Morton wrote: > > > 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 > > Both can be detected from you .config and we could see HZ as needed > there and everyone else could avoid this surely? > While reading this thread it occoured to me that perhaps what we really want (besides sub HZ timers) might be for the kernel to auto-tune HZ? Would it make sense to introduce a new config option (say CONFIG_HZ_AUTO) that when selected does something like this at boot: if (running_on_a_laptop()) { set_HZ_to(250); } else if (running_on_large_NUMA_box()) { set_HZ_to_100(); } else if (running_on_multimedia_box() { set_HZ_to_1000(); } else { set_HZ_to_some_other_sane_default(); } and if user wants to not use the auto detection they can select a certain HZ in their .config instead of CONFIG_HZ_AUTO. Just wanted to throw the idea up in the air in case it made sense. Feel free to pick it apart or simply ignore it. :-) -- Jesper Juhl Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html