From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750853AbWFRKIm (ORCPT ); Sun, 18 Jun 2006 06:08:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750894AbWFRKIm (ORCPT ); Sun, 18 Jun 2006 06:08:42 -0400 Received: from mail31.syd.optusnet.com.au ([211.29.132.102]:43203 "EHLO mail31.syd.optusnet.com.au") by vger.kernel.org with ESMTP id S1750853AbWFRKIl (ORCPT ); Sun, 18 Jun 2006 06:08:41 -0400 From: Con Kolivas To: Willy Tarreau Subject: Re: [ckpatch][15/29] hz-no_default_250.patch Date: Sun, 18 Jun 2006 20:08:31 +1000 User-Agent: KMail/1.9.3 Cc: linux list , ck list References: <200606181732.48952.kernel@kolivas.org> <20060618074247.GF13255@w.ods.org> In-Reply-To: <20060618074247.GF13255@w.ods.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200606182008.31788.kernel@kolivas.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sunday 18 June 2006 17:42, Willy Tarreau wrote: > Hi Con, > > On Sun, Jun 18, 2006 at 05:32:48PM +1000, Con Kolivas wrote: > > Make 250 HZ a value that is not selected by default and give some better > > recommendations in help. > > > > Signed-off-by: Con Kolivas > > > > kernel/Kconfig.hz | 15 +++++++++------ > > 1 files changed, 9 insertions(+), 6 deletions(-) > > > > Index: linux-ck-dev/kernel/Kconfig.hz > > =================================================================== > > --- linux-ck-dev.orig/kernel/Kconfig.hz 2006-06-18 15:23:58.000000000 > > +1000 +++ linux-ck-dev/kernel/Kconfig.hz 2006-06-18 15:24:28.000000000 > > +1000 @@ -21,14 +21,17 @@ choice > > help > > 100 HZ is a typical choice for servers, SMP and NUMA systems > > with lots of processors that may show reduced performance if > > - too many timer interrupts are occurring. > > + too many timer interrupts are occurring. Laptops may also show > > + improved battery life. > > > > - config HZ_250 > > + config HZ_250_NODEFAULT > > bool "250 HZ" > > help > > - 250 HZ is a good compromise choice allowing server performance > > - while also showing good interactive responsiveness even > > - on SMP and NUMA systems. > > + 250 HZ is a lousy compromise choice allowing server interactivity > > + while also showing desktop throughput and no extra power saving on > > + laptops. Good for when you can't make up your mind. > > + > > + Recommend 100 or 1000 instead. > > In fact, I use this value (250 Hz) on servers because it provides slightly > finer scheduling precision than 100 Hz without the performance impact of > 1000 Hz. It also has the advantage that conversions between ms<->jiffies > are performed by bit shifts only and no divide nor multiply. I really do > not notice any performance hit between 100 and 250 Hz, while I do between > 250 and 1000. Thanks for your perspective. I found performance hits on computational tasks with 250 vs 100 but your finer precision makes perfect sense. -- -ck