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	Wed, 1 Oct 1997 11:16:42 +0930 (CST)
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Date: Wed, 1 Oct 1997 11:16:41 +0930
From: Greg Lehey <grog@lemis.com>
To: Changho Choi <chchoi@mmlab.snu.ac.kr>
Cc: freebsd-questions@FreeBSD.ORG
Subject: Re: kernel programming in 4.3BSD
References: <3431A605.35AEBDE1@mmlab.snu.ac.kr>
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In-Reply-To: <3431A605.35AEBDE1@mmlab.snu.ac.kr>; from Changho Choi on Wed, Oct 01, 1997 at 10:23:17AM +0900
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On Wed, Oct 01, 1997 at 10:23:17AM +0900, Changho Choi wrote:
> hello there!
> I have some questions, if you know about those, reply for me please.
> (I use 4.3BSD....)

Really?  Which version?

>      1. I want to know how long one processor occupies CPU before
> happening context  switching. In other words, how often does context
> switching
> happen. how can I change that time?(context switching interval)

On the VAX, 100 ms.

>      2. Is there any way to use math fuctions(for example,  log(),
> sqrt() functions...) in kernel?

I think this is a Bad Idea.  But if you insist, you can compile them
in.

>      3. Do you know how can I delay the message which pass by the
> kernel?
>          I wanna delay the message for some time in kernel.

I don't know what you mean by this.

4.3BSD was introduced in 1987, and it's pretty much obsolete.  If you
want to find details, I'd recommend that you read "The Design and
Implementation of the 4.3BSD UNIX Operating System", by Sam Leffler,
Kirk McKusick, Mike Karels and John Quarterman (Addison Wesley, ISBN
0-201-06196-1).

On the other hand, if you want a modern BSD system, and you have the
appropriate hardware, I'd recommend that you get hold of FreeBSD,
which bases on 4.4BSD.

Greg