From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262092AbULLQiF (ORCPT ); Sun, 12 Dec 2004 11:38:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262089AbULLQhk (ORCPT ); Sun, 12 Dec 2004 11:37:40 -0500 Received: from gprs214-177.eurotel.cz ([160.218.214.177]:18051 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S262088AbULLQgH (ORCPT ); Sun, 12 Dec 2004 11:36:07 -0500 Date: Sun, 12 Dec 2004 17:35:47 +0100 From: Pavel Machek To: Andrea Arcangeli Cc: linux-kernel@vger.kernel.org Subject: Re: dynamic-hz Message-ID: <20041212163547.GB6286@elf.ucw.cz> References: <20041211142317.GF16322@dualathlon.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041211142317.GF16322@dualathlon.random> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.6+20040722i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > The below patch allows to set the HZ dynamically at boot time with > command line parameter. HZ=1000 HZ=100 HZ=333 any other value just works > (though certain value may cause more or less drift to the system time > advance/decrease). > > Is there any interest from the mainline developers to merge this into > 2.6? I'm getting requests for this feature being forward ported to > 2.6 (both for batch jobs and for the powersaved that can trim the hz > down to 80mhz). It should be up to the user to choose the HZ like it was > in 2.4-aa. > > This patch is quite intrusive since many HZ visible to userspace have to > be converted to USER_HZ, and most important because HZ isn't available > at compile time anymore and every variable in function of HZ must be > either changed to be in function of USER_HZ or it must be initialized at > runtime. The code has debugging code (optional at compile time) so that > I can guarantee that there cannot be any regression. > > Technically this makes a lot of sense to me (well, you can guess why I > implemented it in the first place), at least in archs where one cannot > reprogram the timer chip in a performant way (to stop timer ticks > completely until the next posted timer). This is in production for years > in SLES8 btw. > > http://www.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.23aa3/9999_zzz-dynamic-hz-5.gz It certainly helps with singing capacitors... What is overhead of this? Pavel -- People were complaining that M$ turns users into beta-testers... ...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!