From owner-freebsd-stable  Tue May  1  0:18:18 2001
Delivered-To: freebsd-stable@freebsd.org
Received: from netau1.alcanet.com.au (ntp.alcanet.com.au [203.62.196.27])
	by hub.freebsd.org (Postfix) with ESMTP id 0482637B43C
	for <freebsd-stable@FreeBSD.ORG>; Tue,  1 May 2001 00:18:14 -0700 (PDT)
	(envelope-from jeremyp@gsmx07.alcatel.com.au)
Received: from mfg1.cim.alcatel.com.au (mfg1.cim.alcatel.com.au [139.188.23.1])
	by netau1.alcanet.com.au (8.9.3 (PHNE_22672)/8.9.3) with ESMTP id RAA06049;
	Tue, 1 May 2001 17:18:10 +1000 (EST)
Received: from gsmx07.alcatel.com.au by cim.alcatel.com.au
 (PMDF V5.2-32 #37641) with ESMTP id <01K322S0U5Q8RX6X00@cim.alcatel.com.au>;
 Tue, 1 May 2001 17:18:09 +1100
Received: (from jeremyp@localhost)	by gsmx07.alcatel.com.au (8.11.1/8.11.1)
 id f417I7x87104; Tue, 01 May 2001 17:18:08 +1000 (EST envelope-from jeremyp)
Content-return: prohibited
Date: Tue, 01 May 2001 17:18:07 +1000
From: Peter Jeremy <peter.jeremy@alcatel.com.au>
Subject: Re: problem with plip stealing clock
In-reply-to: <3AED84DB.8D241BCF@webmail.bmi.net>; from jmcoopr@webmail.bmi.net
 on Mon, Apr 30, 2001 at 08:29:31AM -0700
To: John Merryweather Cooper <jmcoopr@webmail.bmi.net>
Cc: FreeBSD-STABLE Mailing List <freebsd-stable@FreeBSD.ORG>
Mail-Followup-To: John Merryweather Cooper <jmcoopr@webmail.bmi.net>,
	FreeBSD-STABLE Mailing List <freebsd-stable@FreeBSD.ORG>
Message-id: <20010501171807.M59150@gsmx07.alcatel.com.au>
MIME-version: 1.0
Content-type: text/plain; charset=us-ascii
Content-disposition: inline
User-Agent: Mutt/1.2.5i
References: <3AED84DB.8D241BCF@webmail.bmi.net>
Sender: owner-freebsd-stable@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

On 2001-Apr-30 08:29:31 -0700, John Merryweather Cooper <jmcoopr@webmail.bmi.net> wrote:
>While using my main workstation as a local FTP for my laptop over plip,
>I noticed that FreeBSD was losing track of time at a prodigious rate.

PLIP receives/transmits each IP packet inside a loop at splhigh().
If either system is slow, or the MTU is too high, the time taken to
transfer each packet can exceed 1 tick - meaning that clock interrupt
is lost.  Other PIO peripherals (ethernet or disk) will aggravate the
problem.

I did have the problem with PLIP between my 386 laptop and 486 desktop
until I reduced the MTU to 512.

Have you considered using a PPP link running at 115.2kbps instead?
You will find it a lot more CPU friendly.

Peter

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