From owner-freebsd-hackers  Mon Jun 18 10:57:28 2001
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Date: Mon, 18 Jun 2001 10:57:20 -0700 (PDT)
From: Matt Dillon <dillon@earth.backplane.com>
Message-Id: <200106181757.f5IHvKK16658@earth.backplane.com>
To: "Ashutosh S. Rajekar" <asr@softhome.net>
Cc: freebsd-hackers@FreeBSD.ORG
Subject: Re: max kernel memory
References:  <Pine.LNX.4.21.0106181749030.1209-100000@vangogh.indranetworks.com>
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:Hi,
:
:I'm trying to give the kernel (4.0-RELEASE) 2Gb of memory to work with. I
:can afford to have 4Gb of physical memory on one of my servers, and hence
:the experiments.
:
:Is it safe to play around with KERNBASE, and get away without breaking 
:code ? Is there any other advisable method if this one is risky ?
:
:-ASR

    Yes, you can change KERNBASE.  I'm not entirely sure but I believe if
    you have an old set of bootblocks you may have to reinstall them to 
    get a set that is kernbase-agnostic.  e.g. the disklabel -B command on
    the appropriate slice.

    DG changed KERNBASE a while back to reserve a gigabyte of VM for the
    kernel.  This should be sufficient on a 4G machine but it depends where
    your resources are going.  If your server's resources are user-process
    centric then you don't need to change KERNBASE.  If your server's
    resources are network-mbuf centric then you may have to give the kernel
    more KVM (e.g. like 2GB instead of 1GB... 0x80000000 instead of
    0xC0000000).  But be careful.  The more KVM reserved for the kernel, the
    less VM is available for user processes to allocate and mmap.

    I'm sure people who run 4G machines can give you better information, I've
    never run anything larger then 2G myself, though expect down the line
    I'll begin needing 4G machines to support larger databases.

						-Matt

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