Virtual memory usage with XP

[Randy Harris]

I rather desperately need some information and am hopeful that someone here
can help.

I have a user that is "running out of memory" on XP Pro SP2. It was my
understanding that, being a 32 bit OS, XP could only address a total of 4GB
memory, combined virtual and physical. A co-worker insists that this is
wrong, the 4GB limit is per process, not the entire system. The system has
2GB of RAM, so I said that having a pagefile larger than 2GB would not help.
This person says that he has set the pagefile larger and the system uses the
additional virtual memory.

I know that processes can reserve more virtual memory than they actually
use. Is it the reserve that extends beyond 4GB?

Who is right? Or where can I find something published, preferably by
Microsoft, that would make this clear. Please straighten me out.

 

[dave xnet]

I rather desperately need some information and am hopeful that someone here
can help.

I have a user that is "running out of memory" on XP Pro SP2. It was my
understanding that, being a 32 bit OS, XP could only address a total of 4GB
memory, combined virtual and physical. A co-worker insists that this is
wrong, the 4GB limit is per process, not the entire system. The system has
2GB of RAM, so I said that having a pagefile larger than 2GB would not help.
This person says that he has set the pagefile larger and the system uses the
additional virtual memory.

I know that processes can reserve more virtual memory than they actually
use. Is it the reserve that extends beyond 4GB?

Who is right? Or where can I find something published, preferably by
Microsoft, that would make this clear. Please straighten me out.

It's my understanding 4GB is the RAM limit for xp,
also, 4GB is the virtual address space size per process.
Look here for more:
http://support.microsoft.com/default.aspx?scid=kb;en-us;555223

Dave

 

[Guest]

4GB of ram memory.Also,you should set to "let system manage" in system
properties,you'll find it sets as microsoft recomends 1 1/2 X the amount of
ram.You can also disable the pagingExecutive which makes the system
use ram memory more than paging.You'll find that in regedit/local machine/
system/currentcontrolset/control/sessionmanagment/open memorymanagment.
L.click on DisablePagingExecutive Go to edit,modify,set to 1 from 0 Close
out
regedit.You can see the diffrence in task manager-performance..

 

[Rick \Nutcase\ Rogers]

Hi Randy,

The maximum addressable memory is 4GB in the 32 bit version, and that's for
the entire system, not per process (your co-worker has no clue what he's
talking about). Here is a reference for you:
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

On virtual memory, from the late MVP Alex Nichol:
http://aumha.org/win5/a/xpvm.php

--
Best of Luck,

Rick Rogers, aka "Nutcase" - Microsoft MVP

Windows help - www.rickrogers.org

 

[Plato]

I have a user that is "running out of memory" on XP Pro SP2. It was my

With what app? eg Photoshop will show that message if you have less than
1 gig installed.

 

[Randy Harris]

I'm having some trouble comprehending all of this. In the MS article that
Dave posted a link to, I think it says that:

1) XP does indeed have a 4GB address space limit (and a 4GB RAM limit)
but
2) The address space is split between 2GB for the kernel and 2GB for
process, with each process getting its own 2GB address space.

That seems to suggest that XP could use more than 4GB total virtual memory
(RAM and pagefile combined)

Am I misinterpreting what it says here?

http://support.microsoft.com/default.aspx?scid=kb;en-us;555223

 

[dave xnet]

I'm having some trouble comprehending all of this. In the MS article that
Dave posted a link to, I think it says that:

1) XP does indeed have a 4GB address space limit (and a 4GB RAM limit)
but
2) The address space is split between 2GB for the kernel and 2GB for
process, with each process getting its own 2GB address space.

That seems to suggest that XP could use more than 4GB total virtual memory
(RAM and pagefile combined)

Am I misinterpreting what it says here?

http://support.microsoft.com/default.aspx?scid=kb;en-us;555223

I'd always thought that in the Windows 9x, the processes did indeed
share the memory. In NT/win2k/XP, virtual memory was improved so
that it was multiple. Each process had it's own address space.
As the article mentions 2gb of the 4gb is private to the process,
while 2gb is common to all.
Dave

 

[Rick \Nutcase\ Rogers]

Hi Randy,

You're misinterpreting it. The 2GB for private space means that there is a
total of 2GB available for each process to have its own allocation - not
that each one gets 2GB of allocation.

--
Best of Luck,

Rick Rogers, aka "Nutcase" - Microsoft MVP

Windows help - www.rickrogers.org

 

[Tim Slattery]

I rather desperately need some information and am hopeful that someone here
can help.

I have a user that is "running out of memory" on XP Pro SP2. It was my
understanding that, being a 32 bit OS, XP could only address a total of 4GB
memory, combined virtual and physical. A co-worker insists that this is
wrong, the 4GB limit is per process, not the entire system.

A 32-bit computer has a 32-bit address space. That means that it can
address 2**32 bytes, which works out to 4,294,967,296. So that's the
limit for physical RAM such a machine can handle.

WinXP has a virtual memory system. That allows it to make 2**32 bytes
of virtual memory available to each process that's running. Each
process thinks it sees a full 4,294,967,296 bytes of storage. The OS
keeps half of this virtual space for itself and makes the other half
available to the process.

The virtual memory manager makes sure that pieces of storage that are
needed *now* are in physical RAM. Other parts are kept in the swap
file until they're needed. There is continual traffic back and forth
between RAM and the swap file to make this work properly.

The system has
2GB of RAM, so I said that having a pagefile larger than 2GB would not help.
This person says that he has set the pagefile larger and the system uses the
additional virtual memory.

The virtual memory system is good at this. It's best to let Windows
manage the swap file.

 

[Randy Harris]

Hi Randy,

You're misinterpreting it. The 2GB for private space means that there is a
total of 2GB available for each process to have its own allocation - not
that each one gets 2GB of allocation.

--
Best of Luck,

Rick Rogers, aka "Nutcase" - Microsoft MVP

Windows help - www.rickrogers.org

Sorry for being so dense on this.

But if each process can potentially allocate 2GB, wouldn't the total used
memory potentially be greater than 4GB? I guess the answer that I am really
looking for, is this. On a system with 2GB of RAM, is it potentially
helpful to have more than 2GB of pagefile?

 

[Jim]

Sorry for being so dense on this.

But if each process can potentially allocate 2GB, wouldn't the total used
memory potentially be greater than 4GB? I guess the answer that I am
really
looking for, is this. On a system with 2GB of RAM, is it potentially
helpful to have more than 2GB of pagefile?

The answer to your first question is No. Only a 4gb address space is
effective at any given time.
The answer to your second question is Perhaps.
Jim