From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 10 Apr 2002 01:48:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 10 Apr 2002 01:48:06 -0400 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:53520 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id convert rfc822-to-8bit; Wed, 10 Apr 2002 01:48:06 -0400 To: linux-kernel@vger.kernel.org From: "H. Peter Anvin" Subject: Re: nanosleep Date: 9 Apr 2002 22:47:42 -0700 Organization: Transmeta Corporation, Santa Clara CA Message-ID: In-Reply-To: <20020410044243.2916.qmail@fastermail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Disclaimer: Not speaking for Transmeta in any way, shape, or form. Copyright: Copyright 2002 H. Peter Anvin - All Rights Reserved Content-Transfer-Encoding: 8BIT X-MIME-Autoconverted: from 8bit to quoted-printable by deepthought.transmeta.com id g3A5lhN19588 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Followup to: <20020410044243.2916.qmail@fastermail.com> By author: "mark manning" In newsgroup: linux.dev.kernel > > thanx - how much of a difference should i expect - i know the > syscall is asking for at least the required ammount but that the > task switcher might not give me control back for a while after the > requested delay but i was expecting to be a little closer to what i > had asked for - this isnt critical of corse but i would like to know > what to expect. > Read the man page: BUGS The current implementation of nanosleep is based on the normal kernel timer mechanism, which has a resolution of 1/HZ s (i.e, 10 ms on Linux/i386 and 1 ms on Linux/Alpha). Therefore, nanosleep pauses always for at least the speci­ fied time, however it can take up to 10 ms longer than specified until the process becomes runnable again. For the same reason, the value returned in case of a delivered signal in *rem is usually rounded to the next larger mul­ tiple of 1/HZ s. As some applications require much more precise pauses (e.g., in order to control some time-critical hardware), nanosleep is also capable of short high-precision pauses. If the process is scheduled under a real-time policy like SCHED_FIFO or SCHED_RR, then pauses of up to 2 ms will be performed as busy waits with microsecond precision. -hpa -- at work, in private! "Unix gives you enough rope to shoot yourself in the foot." http://www.zytor.com/~hpa/puzzle.txt