Microsoft KB Archive/264450

= Reduced working set size after installing Windows NT Service Pack 6a =

Article ID: 264450

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT 4.0 Service Pack 6
 * Microsoft Windows NT 4.0 Service Pack 6a
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Enterprise Edition
 * Microsoft Windows NT 4.0 Service Pack 6a

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This article was previously published under Q264450



IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SYMPTOMS
The upper limit of a program's minimum working set can be significantly less on a Windows NT 4.0 Service Pack 6a-based computer than what it may be when you are running Windows NT 4.0 Service Pack 5 or earlier.



CAUSE
Windows NT 4.0 Service Pack 6 addressed an issue where a user-mode program could request more physical memory than what is actually installed on the local computer. This could prevent the non-paged pool from expanding, and this can cause the system processes to run out of memory.



RESOLUTION
A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix should have the following file attributes or later:

 Date      Time               Size       File name      Platform --- 11/03/2000  05:31p           956,672    Ntkrnlmp.exe   Intel 11/03/2000 05:30p           936,384    Ntoskrnl.exe   Intel 11/03/2000 05:27p           1,409,216  Ntkrnlmp.exe   Alpha 11/03/2000 05:27p           1,385,216  Ntoskrnl.exe   Alpha



STATUS
Microsoft has confirmed that this is a problem in Windows NT 4.0 SP6a.



MORE INFORMATION
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

The memory manager in Windows NT 4.0 Service Pack 6 allows for non-paged pool memory to grow to its maximum size before allowing a program to increase its minimum working set size.

By reducing the maximum size of the non-paged pool, programs will be able to receive a larger working set size. The non-paged pool can be reduced by configuring the following new NonPagedPoolMaximumPercent registry entry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

Value Name: NonPagedPoolMaximumPercent

Data Type: REG_DWORD

Radix: Decimal

Data: 0 or 5 - 80

0 = Keeps the old behavior (default)

5 - 80 = The percentage of RAM that is allowed to be non-paged pool.

It is important to understand that excessively reducing the size of the non-paged pool may prevent Windows NT from functioning correctly. If the non-paged pool becomes exhausted, Windows NT generates Stop error messages. The Stop errors that are most likely to occur if the non-paged pool becomes exhausted include Stop 0x4D NO_PAGES_AVAILABLE, Stop 0x41 MUST_SUCCEED_POOL_EMPTY or other Stop error messages.

If the NonPagedPoolMaximumPercent registry value is to be modified from the default value of 0, you should determine the current non-paged pool usage. You can do so by monitoring the following memory counter with Performance Monitor over a period of time. Examine the counter memory / non-paged pool, and find the maximum size it grows to. Use this as the minimum size the non-paged pool should be set to. However it would be strongly recommended to allocate more non-paged pool memory to allow for system usage changes.

The problem with a reduced working set size is very unique, and unless a program requests an increase of its minimum working set size very significantly this problem will not be noticed.

Keywords: kbbug kbfix kbqfe kbenv kbhotfixserver KB264450

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