From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423697AbWKHVH1 (ORCPT ); Wed, 8 Nov 2006 16:07:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423784AbWKHVH1 (ORCPT ); Wed, 8 Nov 2006 16:07:27 -0500 Received: from outpipe-village-512-1.bc.nu ([81.2.110.250]:15851 "EHLO lxorguk.ukuu.org.uk") by vger.kernel.org with ESMTP id S1423697AbWKHVHZ (ORCPT ); Wed, 8 Nov 2006 16:07:25 -0500 Subject: Re: [PATCH] HZ: 300Hz support From: Alan Cox To: Arjan van de Ven Cc: linux-kernel@vger.kernel.org, akpm@osdl.org In-Reply-To: <1163018898.3138.388.camel@laptopd505.fenrus.org> References: <1163018557.23956.92.camel@localhost.localdomain> <1163018898.3138.388.camel@laptopd505.fenrus.org> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Wed, 08 Nov 2006 21:12:01 +0000 Message-Id: <1163020321.23956.96.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.2 (2.6.2-1.fc5.5) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ar Mer, 2006-11-08 am 21:48 +0100, ysgrifennodd Arjan van de Ven: > > I'd argue we should remove 250 and add 300, but that might be excess > > disruption for now. > > > the last time 300 was proposed the counter argument was that it was > lousy in terms of PIT rounding... did you check that out? It keeps time better than 250 when I tried it. It is not perfect but then the PIT runs at a stupid rate so any choice is a little bit off. I think there might be a better argument anyway for making HZ fixed at 1000 and adding a boot time parameter/sysctl value which is a "ticks divisor", so on a server you can do echo "10" >/proc/sys/tick_granularity and jiffies bumps in 10s 1/10th as often. That needs someone who understands the maths and the behaviour of the time slew and xntp stuff to do the job right though, and that isn't me. Alan