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Date:      28 Apr 1999 10:37:37 +0200
From:      Dag-Erling Smorgrav <des@flood.ping.uio.no>
To:        Didier Derny <didier@omnix.net>
Cc:        hackers@FreeBSD.ORG
Subject:   Re: large shared memory (increasing kvm)
Message-ID:  <xzpn1zt5eem.fsf@flood.ping.uio.no>
In-Reply-To: Didier Derny's message of "Fri, 23 Apr 1999 16:37:19 %2B0200 (CEST)"
References:  <Pine.BSF.3.96.990423163019.3173A-100000@idefix>

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Didier Derny <didier@omnix.net> writes:
> for the SQL server, I need a large shared memory (SHMMAXPGS=9216)
> I have maxusers = 512

You shouldn't. Such as it is, your kernel can't properly cope with
values of maxusers greater than 64. You need a larger kvm to handle
that.

> the memory is actually of 256Mb and will be increased to 1Gb
> 
> the kernel is still a.out
> 
> [I have no possibility to stop the machine to upgrade to 3.1-RELEASE or
> 3.1-STABLE (upgrade planned in july/august)]

There is a FAQ entry (13.15) on modifying the size of the kernel
virtual address space. However:

 a) doing so will break binary compatibility with BSD/OS unless you
    also apply John Polstra's patches or upgrade to 3.1.

 b) you will need to upgrade your boot blocks and loader to cope with
    the kvm size change; you have to change the load address as well
    as the kvm size, and the 3.0-RELEASE.

> (I'm running FreeBSD 3.0-RELEASE on a dual pentium II machine
> [ASUS P2B mother board] everything works just fine except that
> we need to largely increase the shared memories and the  semaphores])

Running 3.0-RELEASE on a mission-critical database server? Bad dog,
bad! No bone for you today!

> is VM_KMEM_SIZE working with FreeBSD-3.0-RELEASE ?

I *think* so, but I've never frobbed it, so I can't really comment.

> what value would you suggest ?

1 GB, which is the default in 3.1 and 4.0 now. Just follow the
instructions in the FAQ.

DES
-- 
Dag-Erling Smorgrav - des@flood.ping.uio.no


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