Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262867AbUCPFyL (ORCPT ); Tue, 16 Mar 2004 00:54:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262868AbUCPFyK (ORCPT ); Tue, 16 Mar 2004 00:54:10 -0500 Received: from alt.aurema.com ([203.217.18.57]:19359 "EHLO smtp.sw.oz.au") by vger.kernel.org with ESMTP id S262867AbUCPFxj (ORCPT ); Tue, 16 Mar 2004 00:53:39 -0500 Message-ID: <40569655.2030802@aurema.com> Date: Tue, 16 Mar 2004 16:53:25 +1100 From: Peter Williams Organization: Aurema Pty Ltd User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20030225 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andi Kleen CC: linux-kernel@vger.kernel.org Subject: Re: finding out the value of HZ from userspace References: <1zkOe-Uc-17@gated-at.bofh.it> <1zl7M-1eJ-43@gated-at.bofh.it> <1zn9p-3mW-5@gated-at.bofh.it> <1znj5-3wM-15@gated-at.bofh.it> <1AaWr-655-7@gated-at.bofh.it> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1384 Lines: 33 Andi Kleen wrote: > Peter Williams writes: > > >>This horrible hack of converting all tick values to 100 (from 1000) >>for export to user space because a large number of user space programs >>assume that HZ is 100 would NOT be necessary if there was a mechanism >>whereby user space programs could find out how many ticks there are in >>a second instead of having to make assumptions. > > > Already exists for a long time - AT_CLKTCK. glibc has a nice wrapper > for it too (sysconf) So it does and POSIX.1 (_SC_CLK_TCK) compliant as well. Unfortunately, the presence of this functionality makes it VERY difficult to understand why ticks are being converted from HZ==1000 values to HZ=100 values when they are being exported to user space especially as this conversion throws away precision. Can anyone enlighten me? Peter -- Dr Peter Williams, Chief Scientist peterw@aurema.com Aurema Pty Limited Tel:+61 2 9698 2322 PO Box 305, Strawberry Hills NSW 2012, Australia Fax:+61 2 9699 9174 79 Myrtle Street, Chippendale NSW 2008, Australia http://www.aurema.com - 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/