From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759893Ab0LNUQL (ORCPT ); Tue, 14 Dec 2010 15:16:11 -0500 Received: from lennier.cc.vt.edu ([198.82.162.213]:41362 "EHLO lennier.cc.vt.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759260Ab0LNUQJ (ORCPT ); Tue, 14 Dec 2010 15:16:09 -0500 X-Mailer: exmh version 2.7.2 01/07/2005 with nmh-1.3-dev To: Peter Zijlstra Cc: Wu Fengguang , Andrew Morton , Jan Kara , Dave Chinner , Christoph Hellwig , Trond Myklebust , "Theodore Ts'o" , Chris Mason , Mel Gorman , Rik van Riel , KOSAKI Motohiro , Greg Thelen , Minchan Kim , linux-mm , "linux-fsdevel@vger.kernel.org" , LKML Subject: Re: [PATCH 16/35] writeback: increase min pause time on concurrent dirtiers In-Reply-To: Your message of "Tue, 14 Dec 2010 19:55:08 +0100." <1292352908.13513.376.camel@laptop> From: Valdis.Kletnieks@vt.edu References: <20101213144646.341970461@intel.com> <20101213150328.284979629@intel.com> <15881.1292264611@localhost> <20101214065133.GA6940@localhost> <14658.1292352152@localhost> <1292352908.13513.376.camel@laptop> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1292357637_5019P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Tue, 14 Dec 2010 15:13:57 -0500 Message-ID: <20252.1292357637@localhost> X-Mirapoint-Received-SPF: 128.173.14.107 localhost Valdis.Kletnieks@vt.edu 2 pass X-Mirapoint-IP-Reputation: reputation=neutral-1, source=Fixed, refid=n/a, actions=MAILHURDLE SPF TAG X-Junkmail-Status: score=10/50, host=dagger.cc.vt.edu X-Junkmail-Signature-Raw: score=unknown, refid=str=0001.0A02020A.4D07D007.003F,ss=1,fgs=0, ip=0.0.0.0, so=2010-07-22 22:03:31, dmn=2009-09-10 00:05:08, mode=single engine X-Junkmail-IWF: false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --==_Exmh_1292357637_5019P Content-Type: text/plain; charset="us-ascii" Content-Id: <20222.1292357614.1@localhost> On Tue, 14 Dec 2010 19:55:08 +0100, Peter Zijlstra said: > 10*HZ = 10 seconds > (10*HZ) / 1024 ~= 10 milliseconds from include/asm-generic/param.h (which is included by x86) #ifdef __KERNEL__ # define HZ CONFIG_HZ /* Internal kernel timer frequency */ # define USER_HZ 100 /* some user interfaces are */ # define CLOCKS_PER_SEC (USER_HZ) /* in "ticks" like times() */ #endif Note that HZ isn't USER_HZ or CLOCKS_PER_SEC - it's CONFIG_HZ, which last I checked is still user-settable. If not, then there needs to be a massive cleanup of Kconfig and defconfig: % grep HZ .config CONFIG_NO_HZ=y # CONFIG_HZ_100 is not set # CONFIG_HZ_250 is not set # CONFIG_HZ_300 is not set CONFIG_HZ_1000=y CONFIG_HZ=1000 So you're not guaranteed that 10*HZ is 10 seconds. 10*USER_HZ, sure. But not HZ. --==_Exmh_1292357637_5019P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFNB9AFcC3lWbTT17ARAiAEAKC0yjII9TJD8lfJXeSnMkXkUjX/VQCfQSRX BtQWcpp8YUP/QPYYfDiFDLk= =Aycg -----END PGP SIGNATURE----- --==_Exmh_1292357637_5019P--