From owner-freebsd-arch Fri Dec 10 13: 6:34 1999 Delivered-To: freebsd-arch@freebsd.org Received: from ns1.yes.no (ns1.yes.no [195.204.136.10]) by hub.freebsd.org (Postfix) with ESMTP id 388491519B for ; Fri, 10 Dec 1999 13:06:08 -0800 (PST) (envelope-from eivind@bitbox.follo.net) Received: from bitbox.follo.net (bitbox.follo.net [195.204.143.218]) by ns1.yes.no (8.9.3/8.9.3) with ESMTP id WAA26970 for ; Fri, 10 Dec 1999 22:06:00 +0100 (CET) Received: (from eivind@localhost) by bitbox.follo.net (8.8.8/8.8.6) id WAA38526 for freebsd-arch@freebsd.org; Fri, 10 Dec 1999 22:05:59 +0100 (MET) Received: from ns.mt.sri.com (ns.mt.sri.com [206.127.79.91]) by hub.freebsd.org (Postfix) with ESMTP id 853E314BC3 for ; Fri, 10 Dec 1999 13:05:14 -0800 (PST) (envelope-from nate@mt.sri.com) Received: from mt.sri.com (rocky.mt.sri.com [206.127.76.100]) by ns.mt.sri.com (8.9.3/8.9.3) with SMTP id OAA26233; Fri, 10 Dec 1999 14:04:08 -0700 (MST) (envelope-from nate@rocky.mt.sri.com) Received: by mt.sri.com (SMI-8.6/SMI-SVR4) id OAA21584; Fri, 10 Dec 1999 14:04:06 -0700 Date: Fri, 10 Dec 1999 14:04:06 -0700 Message-Id: <199912102104.OAA21584@mt.sri.com> From: Nate Williams MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: Chuck Robey Cc: Peter Jeremy , freebsd-arch@freebsd.org Subject: Re: Thread scheduling In-Reply-To: References: <99Dec10.155600est.40337@border.alcanet.com.au> X-Mailer: VM 6.34 under 19.16 "Lille" XEmacs Lucid Reply-To: nate@mt.sri.com (Nate Williams) Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > >That is, is it important at all that all processors be doing the same > > >multithreading task (if it's multithreaded, and wants it) at exactly the > > >same time? > > > > I don't think this is guaranteed anywhere. In any case, IMHO it would > > be virtually impossible for a system to provide such a guarantee - > > consider a system which provided such a guarantee and currently has > > two threads executing on two CPUs. An interrupt then occurs on one > > CPU - what happens to the thread on the other CPU (which hasn't seen > > the interrupt)? What happens if (as a result of the interrupt) a > > higher priority process becomes runnable? > > I can think of several ways for it to be done, so lets concentrate on > whether it's needed or desireable. No and no. If any software relies on it, it's completely broken for Uniprocessor machines, since they can't make any such guarantees. Having multiple threads occuring simultaneous is an effeciency issue, but should never be relied on for correct operation of the algorithms in a general purpose computing platform. Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message