From owner-freebsd-current@FreeBSD.ORG Sun Oct 29 09:24:19 2006 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id A009616A407 for ; Sun, 29 Oct 2006 09:24:19 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [209.31.154.42]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0538543D68 for ; Sun, 29 Oct 2006 09:24:18 +0000 (GMT) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [209.31.154.41]) by cyrus.watson.org (Postfix) with ESMTP id 6524A46B82; Sun, 29 Oct 2006 04:24:14 -0500 (EST) Date: Sun, 29 Oct 2006 09:24:14 +0000 (GMT) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: Lucas James In-Reply-To: <200610291257.11744.Lucas.James@ldjcs.com.au> Message-ID: <20061029090945.P27107@fledge.watson.org> References: <45425D92.8060205@elischer.org> <20061028194125.GL30707@riyal.ugcs.caltech.edu> <200610291257.11744.Lucas.James@ldjcs.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-current@freebsd.org Subject: Re: Comments on the KSE option X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 29 Oct 2006 09:24:19 -0000 On Sun, 29 Oct 2006, Lucas James wrote: > I read what Paul said was that system scope threads have a different > "fairness" than processes. ie: > > If your application requires 1000 threads of execution, you can write it > three ways, with 1000 processes, 1000 system scope threads or 1000 process > scope threads (or a mix of the three). > > This whole "fairness" argument is about making system scope threads have the > same priority as process scope threads. It leaves out the process model. > > The real question here is: are we going to make system scope thread model > fair compared to process scope threaded model, or fair compared to the > separate processes model? > > Yes, the process scope threads are allways going to be the poor man with > regard to priority, but as the kernel doesn't see the threads you can't do > much about it. I think there are at least two core questions being discussed here: (1) Does the "fairness" model currently implemented in the KSE code mean well, but cause significant performance problems in practice for real-world applications? (2) Are the cost and complexity impacts of KSE in kernel architecture outweighed by the flexibility and performance benefits of M:N threading? Now is definitely the time for us to be discussing, measuring, experimenting, etc, because addressing the issues of higher concurrency for 7.0 will depend on having decided on a strategy for our scheduler. Robert N M Watson Computer Laboratory University of Cambridge