Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263210AbUCMWTR (ORCPT ); Sat, 13 Mar 2004 17:19:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263218AbUCMWTR (ORCPT ); Sat, 13 Mar 2004 17:19:17 -0500 Received: from bimba.bezeqint.net ([192.115.104.6]:2433 "EHLO bimba.bezeqint.net") by vger.kernel.org with ESMTP id S263210AbUCMWPF (ORCPT ); Sat, 13 Mar 2004 17:15:05 -0500 Date: Sun, 14 Mar 2004 00:14:19 +0200 From: Micha Feigin To: lkml Subject: Re: finding out the value of HZ from userspace Message-ID: <20040313221418.GF5960@luna.mooo.com> Mail-Followup-To: lkml References: <20040311141703.GE3053@luna.mooo.com> <1079198671.4446.3.camel@laptop.fenrus.com> <4053624D.6080806@BitWagon.com> <20040313193852.GC12292@devserv.devel.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040313193852.GC12292@devserv.devel.redhat.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: 1568 Lines: 39 On Sat, Mar 13, 2004 at 08:38:52PM +0100, Arjan van de Ven wrote: > On Sat, Mar 13, 2004 at 11:34:37AM -0800, John Reiser wrote: > > 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 ? > > > > create_elf_tables() in fs/binfmt_elf.c tells every ELF execve(): > > NEW_AUX_ENT(AT_CLKTCK, CLOCKS_PER_SEC); > > which can be found by crawling through the stack above the pointer > > to the last environment variable. > > Ugh that should say 100 on x86.... > but.. > param.h:# define USER_HZ 100 /* .. some user interfaces are in "ticks" */ > param.h:# define CLOCKS_PER_SEC (USER_HZ) /* like times() */ > ..... > that looks like 100 to me. > When dealing with bdflush and a few other interfaces the values need to be in jiffies which requires knowledge of the kernels notion of HZ not userspace. The other option is to try to push a change to make the interface in centisecs instead of jiffies, question is if it will catch. - 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/