From owner-freebsd-current@FreeBSD.ORG  Fri Oct 14 22:33:44 2005
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: 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 C463416A41F
	for <current@freebsd.org>; Fri, 14 Oct 2005 22:33:44 +0000 (GMT)
	(envelope-from wollman@khavrinen.csail.mit.edu)
Received: from khavrinen.csail.mit.edu (khavrinen.csail.mit.edu [128.30.28.20])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 32CDB43D46
	for <current@freebsd.org>; Fri, 14 Oct 2005 22:33:43 +0000 (GMT)
	(envelope-from wollman@khavrinen.csail.mit.edu)
Received: from khavrinen.csail.mit.edu (localhost.csail.mit.edu [127.0.0.1])
	by khavrinen.csail.mit.edu (8.13.1/8.13.4) with ESMTP id j9EMXgkq032038
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256
	verify=OK CN=khavrinen.csail.mit.edu issuer=Client+20CA);
	Fri, 14 Oct 2005 18:33:42 -0400 (EDT)
	(envelope-from wollman@khavrinen.csail.mit.edu)
Received: (from wollman@localhost)
	by khavrinen.csail.mit.edu (8.13.1/8.13.4/Submit) id j9EMXfMf032035;
	Fri, 14 Oct 2005 18:33:41 -0400 (EDT) (envelope-from wollman)
From: Garrett Wollman <wollman@csail.mit.edu>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-ID: <17232.12869.659397.686840@khavrinen.csail.mit.edu>
Date: Fri, 14 Oct 2005 18:33:41 -0400
To: Bruce Evans <bde@zeta.org.au>
In-Reply-To: <20051015074316.T1260@epsplex.bde.org>
References: <12907.1129286370@critter.freebsd.dk>
	<20051015074316.T1260@epsplex.bde.org>
X-Mailer: VM 7.17 under 21.4 (patch 17) "Jumbo Shrimp" XEmacs Lucid
X-Greylist: Sender DNS name whitelisted, not delayed by milter-greylist-1.6
	(khavrinen.csail.mit.edu [127.0.0.1]);
	Fri, 14 Oct 2005 18:33:42 -0400 (EDT)
X-Spam-Status: No, score=0.0 required=5.0 tests=none version=3.0.2
X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on 
	khavrinen.csail.mit.edu
X-Mailman-Approved-At: Sat, 15 Oct 2005 12:49:20 +0000
Cc: current@freebsd.org
Subject: Re: Call for performance evaluation: net.isr.direct (fwd) 
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 14 Oct 2005 22:33:44 -0000


[Moved to -current as this is no longer net related.]

<<On Sat, 15 Oct 2005 08:28:04 +1000 (EST), Bruce Evans <bde@zeta.org.au> said:

> values of HZ like 1000 -- with hz > stathz it is easy to use a periodic
> itimer to arrange to run about (hz - stathz) / hz of the time without ever
> seeing a statclock tick.

The whole point of statclock was that it was supposed to be an
exponential distribution centered on stathz, not strictly periodic,
precisely to prevent this problem.

With the new APIC clock divider code, we should be able to do this
fairly cheaply and at a higher rate than 128 Hz.  It was originally
developed on SPARC hardware so that architecture ought to be able to
do it easily.

-GAWollman