From owner-freebsd-arch Thu Jan 10 14:45:11 2002 Delivered-To: freebsd-arch@freebsd.org Received: from ns.yogotech.com (ns.yogotech.com [206.127.123.66]) by hub.freebsd.org (Postfix) with ESMTP id 7BA7037B404 for ; Thu, 10 Jan 2002 14:45:08 -0800 (PST) Received: from caddis.yogotech.com (caddis.yogotech.com [206.127.123.130]) by ns.yogotech.com (8.9.3/8.9.3) with ESMTP id PAA08785; Thu, 10 Jan 2002 15:44:52 -0700 (MST) (envelope-from nate@yogotech.com) Received: (from nate@localhost) by caddis.yogotech.com (8.11.6/8.11.6) id g0AMip700398; Thu, 10 Jan 2002 15:44:51 -0700 (MST) (envelope-from nate) From: Nate Williams MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15422.6499.274704.270810@caddis.yogotech.com> Date: Thu, 10 Jan 2002 15:44:51 -0700 To: Terry Lambert Cc: Kelly Yancey , Alfred Perlstein , Nate Williams , Daniel Eischen , Dan Eischen , Peter Wemm , Archie Cobbs , arch@FreeBSD.ORG Subject: Re: Request for review: getcontext, setcontext, etc In-Reply-To: <3C3E1870.1E0DA81F@mindspring.com> References: <3C3E1870.1E0DA81F@mindspring.com> X-Mailer: VM 6.96 under 21.1 (patch 14) "Cuyahoga Valley" XEmacs Lucid Reply-To: nate@yogotech.com (Nate Williams) Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG > > If the context switch overhead is the same (or worse) with a userland > > scheduler, then what are the "effeciency reasons" for having it? Where does > > the userland scheduler reclaim it's lost ground? The only things my limited > > understanding can produce are a number of trivial data structures that can be > > moved from the kernel to userland. :/ > > It seems to me that if {get,set}context involve kernel calls, then any > > userland scheduler would, by definition, require N+1 context switches where N > > is the number of context switches required by a kernel-only scheduler. The > > extra 1 coming from invoking the scheduler context itself. > > Remember that this is only true if someone is stupid enough to > use the FPU, which is only useful for very specific tasks, most > of which are non-threaded. Huh? Methinks Terry needs to make assume the world is just a *teeny* bit larger than his narrow-view. > For graphics and line drawing -- even > curve drawing -- the fast graphics world all uses integer math > and tables. That leave us with special purpose number crunching > that doesn't care incredibly deeply about its significant digits > running away to exponent&mantissa-land. Even simple statistics use FP math. You're implying that FPU should only be used by folks who have a real *NEED* for it, which is humerous considering you're the one who usually bangs on the drum to make FreeBSD useful for more folks. :) Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message