From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760537AbZEGOVT (ORCPT ); Thu, 7 May 2009 10:21:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757388AbZEGOVG (ORCPT ); Thu, 7 May 2009 10:21:06 -0400 Received: from smtp3.ultrahosting.com ([74.213.175.254]:36972 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754005AbZEGOVF (ORCPT ); Thu, 7 May 2009 10:21:05 -0400 Date: Thu, 7 May 2009 10:09:56 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@qirst.com To: Alan Cox cc: akataria@vmware.com, "H. Peter Anvin" , Ingo Molnar , Thomas Gleixner , the arch/x86 maintainers , LKML Subject: Re: [PATCH] x86: Reduce the default HZ value In-Reply-To: <20090505233339.542880f8@lxorguk.ukuu.org.uk> Message-ID: References: <1241462661.412.8.camel@alok-dev1> <4A00ADDE.9000908@zytor.com> <20090505224417.0f00c2f0@lxorguk.ukuu.org.uk> <1241561394.8665.31.camel@alok-dev1> <20090505233339.542880f8@lxorguk.ukuu.org.uk> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 5 May 2009, Alan Cox wrote: > HZ on a tickless system has no meaningful relationship to wakup rates - > which are what I assume you actually care about. Linux is not tickless. It only switches off ticks if a processor is idle. > So do you want to change the precision of poll() and other > functionality ? or do you want to change the wakeup rates and > corresponding virtualisation overhead ? select and poll use timeouts based on high resolution timers. > What measurements have you done that make you think HZ is relevant in a > tickless kernel ? Just reading the code gets you there.