I need to allocate an enormous amount of physical memory
(>80% of system memory) and ensure that is is locked into
physical memory.
I've considered MmProbeAndLockPages, but if the allocated
memory is seriously fragmented, the MDL may end up being
too large.
Is there another way to ensure that memory allocated from
the PagedPool never gets paged?
-Brett

I'm developing a Windows-based memory test and I need to
allocate as much memory as possible (I meant >80% of
AVAILABLE system memory, sorry). Thus, I need to ensure
that the algorithms used to test memory don't get mixed
up with paging operations. That is why I want to lock
pages in memory.
-Brett

Sorry, but in the virtual-addressing world of WinXP and quite a few
other OSes, this is not a well-formed question.

Consider writing your program to get the maximum amount of virtual
memory. Remove non-essential applicatiosn for the system. Run your
program. That's about the best you can do without going into kernel
mode, and it ought to be a decent test.

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If replying by e-mail, please remove "nospam." from the address.

James Antognini
Windows DDK MVP

"Brett" <elderdodds@yahoo.com> wrote:
That is an incredibly bad idea; there is so much of the memory you can't
test that it would be essentially worthless. The best memory tests take
over the machine through a boot floppy, so that they have 100% control over
100% of the memory. There are several excellent and simple-to-use DOS
extenders available for free download that will allow you do this is a very
useful manner..
--
- Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

On Mon, 14 Jul 2003 22:26:37 -0700, Tim Roberts <timr@probo.com> wrote:

Yes, I've even seen memory test that relocate themselves into the VGA
framebuffer memory and run from there so they can actually test all the
on-board memory.

I am fully aware of all the issues associated with
building a Windows-based memory test. I have worked on a
proprietary DOS-based memory test for quite some time
now. What I really need is an answer to my question about
locking pages in physical memory. If someone has an
answer, I would appreciate a reply.
Thank you,
-Brett

Your best bet would be to use the /maxmem switch on boot.ini
to limit memory to the smallest the system will run in, then map
in that memory in sections to system address space. Of course
this has its own problems including determing how much memory
you have, and not being able to test the low xxxMB of memory,
and requiring reboots if the system is to be used normally.

I have done a partial test of memory over the whole range by doing
non-destructive writes to memory but it sounds like you want more
than that.


Don Burn (MVP, Windows DDK)
Windows 2k/XP/2k3 Filesystem and Driver Consulting

"Brett" <elderdodds@yahoo.com> wrote in message
news:011601c34ae3$e4ddf950$a101280a@phx.gbl...

I don't want the memory I allocate to be paged out. I
want to control memory accesses as well as possible
through test algorithms only.
Thanks,
-Brett

Then you're in need of kernel function, to prevent page stealing,
amongst other things.

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If replying by e-mail, please remove "nospam." from the address.

James Antognini
Windows DDK MVP

"Brett" <elderdodds@yahoo.com> wrote in message
news:011601c34ae3$e4ddf950$a101280a@phx.gbl...
But what exactly are you testing , physical RAM itself or some aspect of
virtual memory/paging?
Can you use PhysicalMemory section - it by definition gives whole physical
memory (?)

- PA

Yeah, I knew about that test, too. The reason I want to
do it completely in Windows is because there are certain
memory events (like power management events) that are
only present in the Windows environment and often
transparent to the user (depending on chipset
implementation). I want to be able to test memory while
operating under the Windows environment.

In the end, I am going to do this and I am going to do it
in Windows.

So, what I'm really after is a way to force pages to lock
into physical memory so I can test them. If anyone has a
solution to this problem, please post it here or email me
directly.
Thank you,
-Brett

I do want to mention that I appreciate all who have
posted on this now lengthy thread. I understand that my
request is quite extraordinary and that there are similar
ways of doing it easier. But, alas, I'm bound to do it
the way I've mentioned (in Windows). I'm still
solutionless, so if you can offer help, let me know.
Thanks again,
Brett

This newsgroup is concerned with the kernel, and one ought to expect
answers that exploit the kernel. Lucky for you, the kernel is the way to
go, and you've been pointed in the direction of using kernel function.
You've been told that's the way to exercise some control over things
that concern you. Since you seem unreceptive to that advice, why keep
asking?

--
If replying by e-mail, please remove "nospam." from the address.

James Antognini
Windows DDK MVP

"Brett" <elderdodds@yahoo.com> wrote in message
news:0c7601c34ba6$2737f9a0$a301280a@phx.gbl...
[...snip...]
OK, if you're determined to go this route..

WARNING THE FOLLOWING IS NOT FOR THE SQUEAMISH, AND WILL MORE THAN LIKELY
CORRUPT YOUR SYSTEM

First there are a few issues that need to be addressed:
1. Not all physical memory is pageable, so how are you going to test those
pages? (I'm assuming that your memory test is destructive (of the memory
contents) and somewhat time consuming).
To get around this, you would have to essentially stop processing on the system,
copy the contents of the page to test, and then change the page table entry to
point to the new page. To stop processing, I would send DPCs to all the CPUs,
and have the DPC set its IRQL to 31, and then spin waiting for all the rest of
the CPUs to do the same thing. When all the CPUs are spinning, then one of the
CPUs should be able to copy the contents of the page into another page (that
you allocated *before* raising to IRQL 31), and then go diddle the page tables
(Landy, don't shoot me!), and then flush the TLB. You could probably use this
technique to run through all of memory.

2. Not all physical memory is accessible (if I remember correctly, the disk
boot/crash dump driver is unmapped while the system is running, to prevent it
from being corrupted)
You'll have to allocate some system page table entries, and then fill them in to
point to the inaccessible pages (see the technique above for making the system
quiescent), and then flush the TLB

You're going to have to spend more than a little time in the debugger and the
Intel documentation to figure out the page tables and page frame data structures
layout. Also, remember that the page tables themselves are pageable.

Good luck - you'll need it. By the way, what company do you work for? I want
to make sure I don't mistakenly buy something from them that has this code in
it.

-Brian

Brian Catlin, Sannas Consulting 310-798-8930
Windows Network, Video, WDM Device Driver Training & Consulting
See WWW.AZIUS.COM for courses and scheduling

Before doing any of the horrible thing recomenede below,
give a look at the output of the debugger command '!pfn 0 8000000F' on KD.
This will give you an idea of which physical pages are used by
the os at the given moment, and which ones are availalbe for you to run
your memory test.
Before you put to spin all the CPUs besides the one you are wishing to use
as a worker,
make sure the code they are spinning on is not going to be touched by your
memory test.
You may argue that the local CPU cache would allow CPUs to spin even if the
physical memory is pulled from underneath them, but you have to be really
careful
on what are the side effects of invalidating caches and TLBs across all the
CPUs
your test will run on.
On the side, if the system is using some megs
of memory for the current working set of the running processes,
you will have to carefully save the page away before testing the undelaying
physical page.
If you can do that one page at time, you may just need one unused physical
page.
Naturally you will have to skip the region of physical memory used by
devices to perform DMA,
unless you disable all the DMA devices before running your test.
If you choose not to pay attention to all these details,
you can limit your test to all the physical pages not currently in use by
the OS
(or reserved by the OS for special purposes)
after you've put the system 'to sleep'.

Honestly, a memory checker is better developed in a minimal bootstrap code,
after the CPU is in protected mode with no paging enabled and no TLB/caching
enabled.
A minimal bootstrap code can be written in less that 20 assembly instruction
(if you target x86),
and then you can jump to your C/C++ code.

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Use of any included script samples are subject to the terms specified at
http://www.microsoft.com/info/cpyright.htm


"Brian Catlin" <brianc@sannas.org> wrote in message
news:Oks##y7SDHA.2276@TK2MSFTNGP10.phx.gbl...

I appreciate the post and your solution is intriguing, but
I am not trying to test all of memory, just as much as I
can get my hands on. The memory errors I'm concerned about
are usually algorithm dependent rather than specific bit
fails. Getting as much memory as possible is best, but
getting the entire array is overkill.

And as for this...
HaHaHa - I can assure you that you'll never buy software
from my company, I'd be afraid to give it to the world and
have to support it.
This is an "Internal Use Only" type of thing.

I can appreciate that this has to be done with the kernel.
That is why I posted this here in the first place. Now, if
you would kindly give me a direction of how to do this
with kernel functions...
-Brett

Thanks, that is one way I have considered doing the test,
but I don't want to overwrite the contents of some other
process's memory. How can I ensure that the memory I'm
testing remains untouched by other processes?
-Brett

"Brett" <elderdodds@yahoo.com> wrote in message
news:08cd01c34bc5$408bf360$a001280a@phx.gbl...
In that case, just grab huge chunks of paged pool and then lock down the pages

-Brian

Brian Catlin, Sannas Consulting 310-798-8930
Windows Network, Video, WDM Device Driver Training & Consulting
See WWW.AZIUS.COM for courses and scheduling

This is essentially what I am asking. Back to the start of
this thread... I want to lock down the pages, but I'm not
sure what else I can use besides MmProbeAndLockPages. I
would use it, but I'm afraid that a heavily fragmented
memory chunk will cause the MDL to be too large and
therefore fail. Isn't there a limit to how much
MmProbeAndLockPages will actually lock?