Date: Wed, 25 Jul 2001 16:24:26 +1000 From: Peter Jeremy <peter.jeremy@alcatel.com.au> To: Matt Dillon <dillon@earth.backplane.com> Cc: arch@FreeBSD.ORG Subject: Re: cvs commit: src/sys/netinet tcp_usrreq.c Message-ID: <20010725162426.R506@gsmx07.alcatel.com.au> In-Reply-To: <200107250516.f6P5GG541239@earth.backplane.com>; from dillon@earth.backplane.com on Tue, Jul 24, 2001 at 10:16:16PM -0700 References: <20010718121851.B26558@dragon.nuxi.com> <20010718214902.H6519-100000@achilles.silby.com> <20010724205513.H5825@dragon.nuxi.com> <200107250516.f6P5GG541239@earth.backplane.com>
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[Cc: trimmed]
On 2001-Jul-24 22:16:16 -0700, Matt Dillon <dillon@earth.backplane.com> wrote:
> I think KVM management has gotten to the point where we might as well
> setup page tables for the entire 1GB, which will cost us 1MB of ram
> for page tables.
This is still a hit for small memory machines. 4.3-RELEASE states
"minimum 16MB RAM" - 1MB a significant slice of this.
> If we do that it will remove or greatly reduce one of
> the many problems we have to deal with.
Accepted. I think the idea of allocating page tables for KVM is
worthwhile. I just think we need to make KVM scalable first.
Would it be practical to move the kernel to the top of memory and have
the KVM space grow down to a size determined by physical RAM (eg KVM
is the same as physical RAM[1], capped to say 2GB) and then allocate
page tables to suit. (This has the added advantage of not needing the
kernel to be re-linked if you need >1GB KVM).
[1] I don't think anything in KVM is currently pageable so it doesn't
make sense to have more KVM than RAM. If this isn't true, or when
we implement pageable KVM, we can increase the KVM to physical RAM
ratio.
Peter
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