From owner-freebsd-smp Thu Dec 7 19:23:41 2000 From owner-freebsd-smp@FreeBSD.ORG Thu Dec 7 19:23:39 2000 Return-Path: Delivered-To: freebsd-smp@freebsd.org Received: from mass.osd.bsdi.com (adsl-63-202-176-64.dsl.snfc21.pacbell.net [63.202.176.64]) by hub.freebsd.org (Postfix) with ESMTP id D7F7C37B400 for ; Thu, 7 Dec 2000 19:23:38 -0800 (PST) Received: from mass.osd.bsdi.com (localhost [127.0.0.1]) by mass.osd.bsdi.com (8.11.0/8.11.1) with ESMTP id eB83WtF00456; Thu, 7 Dec 2000 19:32:55 -0800 (PST) (envelope-from msmith@mass.osd.bsdi.com) Message-Id: <200012080332.eB83WtF00456@mass.osd.bsdi.com> X-Mailer: exmh version 2.1.1 10/15/1999 To: Terry Lambert Cc: smp@FreeBSD.ORG Subject: Re: Netgraph and SMP In-reply-to: Your message of "Fri, 08 Dec 2000 03:11:08 GMT." <200012080311.UAA02374@usr08.primenet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Thu, 07 Dec 2000 19:32:55 -0800 From: Mike Smith Sender: msmith@mass.osd.bsdi.com Sender: owner-freebsd-smp@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org > In Solaris, the entry into the driver would hold a reference, > which would result in the reference count being incremented. > Only modules with a 0 reference count can be unloaded. This > same mechanism is used for vnodes, and for modules on which > other modules depend. It works well, ans is very light weight. The whole problem is that it *isn't* very light weight. The reference count has to be atomic, which means that it ping-pongs around from CPU to CPU, causing a lot of extra cache traffic. OTOH, there's not much we can do about this short of going looking for better multi-CPU reference count implementations once we have time to worry about performance. -- ... every activity meets with opposition, everyone who acts has his rivals and unfortunately opponents also. But not because people want to be opponents, rather because the tasks and relationships force people to take different points of view. [Dr. Fritz Todt] V I C T O R Y N O T V E N G E A N C E To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message