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Date:      Thu, 14 Mar 2002 10:44:54 -0600 (CST)
From:      mark tinguely <tinguely@web.cs.ndsu.nodak.edu>
To:        freebsd-questions@FreeBSD.ORG, wam@HiWAAY.net
Subject:   Re: Maximizing user-process address space under 4.4
Message-ID:  <200203141644.g2EGisl21602@web.cs.ndsu.nodak.edu>
In-Reply-To: <3C900211.EA1EEF62@HiWAAY.net>

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>      I recently installed FreeBSD 4.4 (Wind river, not a copy) on my 933
>  MHz Intel box. I want to use the machine to do finite element analysis &
>  want to be able to address as much of the 4 GB 32 bit address space as
>  possible to run big jobs (I was stuck at 2 GB w/ Linux, that's why
>  FreeBSD). I have talked w/ some people who gave me some suggestions, but
>  most were for 4.5, not 4.4. I can use 2 GB now, but whenever I recompile
>  the kernel w/ larger MAXDSIZ parameter (larger than 2 GB), the compile &
>  install go OK, but the kernel won't boot. Someone said something about
>  trying to cut down on a parameter called KVA_PAGES, but that's 4.5, not
>  4.4. What is the equivalent parameters(s) under 4.4 ? Thanks in advance
>  for your time.

The kernel won't boot because you ran out of Kernel Virtual Memory
because of the high number of disk buffer buffers (which are automatically
calculated to be a percentage of your physical memory).

To fix this problem, either upgrade to FreeBSD 4.5/stable or
The *increase* the kernel virtual address space (which will also
decrease your user virtual address, which is what you do *not* want
to do). The handbook and an -hackers mail from Terry Lambert
(Dec 6, 2001 "Re: 4G phisical memory kernel trap") explains how
to increase the kernel virtual memory.

If you want to look in -hackers mailing list for articles by Matt Dillon
in the Aug 19, 2001 time frame there is an explaination of the problem
and some patches that scale back the number of disk buffers when the
machine has lots of physical memory. BUT I would highly recommend
FreeBSD 4.5/stable over a single patch.

--mark tinguely.

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