Re: Cannot activate sbcl

George Neuner wrote:
On Fri, 09 Nov 2007 12:01:40 -0800, "Dimiter \"malkia\" Stanev"
<malkia@xxxxxxxxx> wrote:

Hi George,

You must be running a 64-bit version of Windows - 32-bit versions are
limited to 4GB page files.
Somehow I've managed to use 16GB and I'm using the 32bit version of Windows XP (Latest service pack, updates, etc), and I was able to use all that memory (e.g. I was able to run 9 copies of the "a.exe" with 1.85GB of memory in each = 16.65GB). My machine has 4GB itself + 16GB virtual memory additional.

Ok, I was just reminded privately that XP Workstation (kind of)
supports PAE.

That could be the case. I've heard of it, but never really thought that Windows XP might use it in 32bit without some extra API calls.

It loooks like we do have some pretty cool machines at work :) - The HP xw8400 desktop:

http://h10010.www1.hp.com/wwpc/us/en/sm/WF05a/12454-12454-296719-307907-296721-1844968.html

Ours are with the Quad-Core Intel Xeon cpu 5355 at 2.66 GHz 8 MB L2 cache 1333 Mhz and custom video cards.

PAE allows access to RAM above 4GB and virtual memory (RAM + page
file) up to 128GB. Applications still are limited to 4GB of addresses
at any one time, but can access RAM above 4GB through AWE, a paging
scheme similar to Expanded memory under DOS (see VirtualAlloc's
MEM_PHYSICAL switch, AllocateUserPhysicalPages, MapUserPhysicalPages).
32-bit server versions of Windows allow more than 4GB of RAM to be
installed so enabling PAE for them makes sense - in addition to use by
applications, the OS can use high RAM to hot swap programs.

However, XP allows only 4GB of RAM regardless of PAE, so AWE doesn't
work. But when PAE is enabled, XP will allow a very large page file
to be created and use the extra space to allow running more programs.
You must enable PAE to get a 4GB configuration on XP (actually to use
3GB of physical RAM) but IMO it really doesn't make sense to
configure an enormous page file. VMM page table entries double in
size under PAE and the swapped pages on disk have to be tracked, so
you're actually giving up a significant bit of memory without gaining
any of the benefits of AWE.

Aha that clears it then. Fortunately all our machines should support it, so I can deploy the hacky mechanism I've described. I'm already using it in an application that servers as quick/dirty replacement for swapping memory-manager that would use another applications virtual memory for address space and through ReadProcessMemory WriteProcessMemory would access it (highly hacked mechanism, that is not recommended for general usage, especially Read/WriteProcessMemory).

I had known about the PAE support in XP, but had dismissed it because
it is crippled and essentially useless from the application's point of
view.

Please forgive me if I got overly pedantic arguing with you.

On the contrary! The information you provided gave me insights into some of the things I thought I knew, and made me read about them again and others.

That's what I like about comp.lang.lisp - you can find people with great knowledge on lots of different topics :)


George
--
for email reply remove "/" from address

Cheers,
malkia
.

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