Test - Please ignore
----- Original Message ----- 
From: "David Schultz" <[EMAIL PROTECTED]>
To: "Terry Lambert" <[EMAIL PROTECTED]>
Sent: Monday, April 22, 2002 6:09 AM
Subject: Re: FreeBSD 4.5-STABLE not easily scalable to large servers ... ?

> Thus spake Terry Lambert <[EMAIL PROTECTED]>:
> > If you want more, then you need to use a 64 bit processor (or use a
> > processor that supports bank selection, and hack up FreeBSD to do
> > bank swapping on 2G at a time, just like Linux has been hacked up,
> > and expect that it won't be very useful).
> I'm guessing that this just means looking at more than 4 GB of memory
> by working with 2 GB frames at a time.  As I recall, David Greenman
> said that this hack would essentially require a rewrite of the VM
> system.  Does this just boil down to using 36 bit physical addresses?
> Are there plans for FreeBSD to support it, or is everyone just waiting
> until 64 bit processors become more common?
> > You can't
> > really avoid that, for the most part, since there's a shared TLB
> > cache that you really don't have opportunity to manage, other than
> > by seperating 4M vs. 4K pages (and 2M, etc., for the Pentium Pro,
> > though variable page granularity is not supported in FreeBSD, since
> > it's not common to most hardware people actually have).
> Does FreeBSD use 4M pages exclusively for kernel memory, as in
> Solaris, or is there a more complicated scheme?
> > If you increase the KVA, then you will decrease the UVA available to
> > user processes.  The total of the two can not exceed 4G.
> In Linux, all of physical memory is mapped into the kernel's virtual
> address space, and hence, until recently Linux was limited to ~3 GB of
> physical memory.  FreeBSD, as I understand, doesn't do that.  So is
> the cause of this limitation that the top half of the kernel has to
> share a virtual address space with user processes?
> I'll have to read those books one of these days when I have time(6).
> Thanks for the info.
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