From owner-freebsd-arch  Thu Jan 10 13:52:47 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 6843537B400
	for <arch@FreeBSD.ORG>; Thu, 10 Jan 2002 13:52:36 -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 OAA06696;
	Thu, 10 Jan 2002 14:52:24 -0700 (MST)
	(envelope-from nate@yogotech.com)
Received: (from nate@localhost)
	by caddis.yogotech.com (8.11.6/8.11.6) id g0ALqFY25912;
	Thu, 10 Jan 2002 14:52:15 -0700 (MST)
	(envelope-from nate)
From: Nate Williams <nate@yogotech.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-ID: <15422.3343.322370.370639@caddis.yogotech.com>
Date: Thu, 10 Jan 2002 14:52:15 -0700
To: Kelly Yancey <kbyanc@posi.net>
Cc: Nate Williams <nate@yogotech.com>,
	Terry Lambert <tlambert2@mindspring.com>,
	Daniel Eischen <eischen@pcnet1.pcnet.com>,
	Dan Eischen <eischen@vigrid.com>, Peter Wemm <peter@wemm.org>,
	Archie Cobbs <archie@dellroad.org>, Alfred Perlstein <bright@mu.org>,
	arch@FreeBSD.ORG
Subject: Re: Request for review: getcontext, setcontext, etc
In-Reply-To: <Pine.BSF.4.21.0201101309200.6849-100000@gateway.posi.net>
References: <15421.64170.308581.606485@caddis.yogotech.com>
	<Pine.BSF.4.21.0201101309200.6849-100000@gateway.posi.net>
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: <freebsd-arch.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-arch>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-arch>
X-Loop: FreeBSD.ORG

> > See above.  Even in 5.0, we're going to have some threads being switched
> > in userland context, while others are switched in the kernel.  (KSE is a
> > hybrid approach that attempts to gain both the effeciency of userland
> > threads with the ability to parallelize the effeciency gains of multiple
> > CPU && I/O processing from kernel threads.
> > 
> > Nate
> > 
> 
>   OK, I'm going to stick my head in and show my ignorance. If {get,set}context
> have to be implemented as system calls, then doesn't that eliminate much, if
> not all, the gains assumed by having a separate userland scheduler?

IMO, yes.

> I mean if we've got to go to the kernel to switch thread contexts, why
> not just have the kernel track all of the threads and restore context
> once, just for the current thread, rather than twice (once for the
> scheduler and another for the scheduler to switch to the current
> thread context)?

For effeciency reasons...



Nate

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-arch" in the body of the message