Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263243AbUCNBI1 (ORCPT ); Sat, 13 Mar 2004 20:08:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263248AbUCNBI0 (ORCPT ); Sat, 13 Mar 2004 20:08:26 -0500 Received: from nils.bezeqint.net ([192.115.104.5]:9417 "EHLO nils.bezeqint.net") by vger.kernel.org with ESMTP id S263243AbUCNBIR (ORCPT ); Sat, 13 Mar 2004 20:08:17 -0500 Date: Sun, 14 Mar 2004 03:07:30 +0200 From: Micha Feigin To: lkml Subject: Re: finding out the value of HZ from userspace Message-ID: <20040314010730.GM5960@luna.mooo.com> Mail-Followup-To: lkml References: <20040311141703.GE3053@luna.mooo.com> <1079198671.4446.3.camel@laptop.fenrus.com> <20040313221018.GE5960@luna.mooo.com> <1079217685.4915.2.camel@laptop.fenrus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1079217685.4915.2.camel@laptop.fenrus.com> User-Agent: Mutt/1.5.5.1+cvs20040105i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1685 Lines: 35 On Sat, Mar 13, 2004 at 11:41:25PM +0100, Arjan van de Ven wrote: > On Sat, 2004-03-13 at 23:10, Micha Feigin wrote: > > On Sat, Mar 13, 2004 at 06:24:31PM +0100, Arjan van de Ven wrote: > > > On Thu, 2004-03-11 at 15:17, Micha Feigin wrote: > > > > Is it possible to find out what the kernel's notion of HZ is from user > > > > space? > > > > It seem to change from system to system and between 2.4 (100 on i386) > > > > to 2.6 (1000 on i386). > > > > > > if you can see 1000 from userspace that is a bad kernel bug; can you say > > > where you find something in units of 1000 ? > > > > I can't see it from user space. Its in the kernel headers. The thing is > > I am working on fixes to laptop mode. The problem is it requires > > changing bdflush and journaled file systems journal flush times. The > > problem is that some of these (bdflush, xfs) expect the value in jiffies > > and not seconds or milliseconds so making the initiation script portable > > requires knowing the value of HZ. > > the kernel side is supposed to use clock_t_to_jiffies() and co for this > to present a unified HZ to userspace. The internal kernel HZ should > *NOT* leak out to usespace. Heck it's quite thinkable that in the future > there will be no such HZ. > > Kernel side doesn't do that at the moment. Even the fixed bdflush interface in 2.6 which has dirty_writeback_centisecs as an example converts it as (dirty_writeback_centisecs * HZ) / 100 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/