PagedPoolSize and NonPagedPoolSize Values in Windows NT

ID: Q126402

The information in this article applies to:

Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0
Microsoft Windows NT Server versions 3.5, 3.51, 4.0
Microsoft Windows 2000 Professional
Microsoft Windows 2000 Server
Microsoft Windows 2000 Advanced Server

SUMMARY

Windows NT calculates NonPagedPoolSize and PagedPoolSize based on the amount of physical memory present in the computer at boot time. This article describes the algorithms used to calculate these values on an x86- based computer.

NOTE: The Windows NT 3.5 Resource kit incorrectly describes PagedPoolSize calculations.

MORE INFORMATION

NonPagedPoolSize and PagedPoolSize are calculated using complex algorithms based on physical memory size. However, you can use the following formulas to approximate these values for an X86-based computer.

Definitions

MinimumNonPagedPoolSize = 256K
MinAdditionNonPagedPoolPerMb = 32K
DefaultMaximumNonPagedPool = 1 MB
MaxAdditionNonPagedPoolPerMb = 400K
PTE_PER_PAGE = 1024
PAGE_SIZE=4096

NonPagedPoolSize Calculation

NonPagedPoolSize = MinimumNonPagedPoolSize + ((Physical MB - 4) * MinAdditionNonPagedPoolPerMB)

EXAMPLE - On a 32 MB x86-based computer:

MinimumNonPagedPoolSize = 256K
NonPagedPoolSize = 256K + ((32 - 4) * 32K) = 1.2 MB

MaximumNonPagedPoolSize = DefaultMaximumNonPagedPool + ((Physical MB - 4) * MaxAdditionNonPagedPoolPerMB)

If MaximumNonPagedPoolSize < (NonPagedPoolSize + PAGE_SIZE * 16),
then MaximumNonPagedPoolSize = (NonPagedPoolSize + PAGE_SIZE * 16)

IF MaximumNonPagedPoolSize >= 128 MB MaximumNonPagedPoolSize = 128 MB

EXAMPLE - On a 32 MB x86-based computer:

MaximumNonPagedPoolSize = 1 MB + ((32 - 4) * 400K) = 12.5 MB

PagedPoolSize Calculation

Size = (2 * MaximumNonPagedPoolSize) / PAGESIZE Size = (Size + (PTE_PER_PAGE - 1)) / PTE_PER_PAGE PagedPoolSize = Size * PAGESIZE * PTE_PER_PAGE IF PagedPoolSize >= 192 MB PagePoolSize = 192 MB EXAMPLE - On a 32 MB x86-based computer:

Size = (2 * 12.5M) / 4096 = 6400
Size = (6400 + (1024 - 1)) / 1024 = 7.25
PagedPoolSize = 7.25 * 4096 * 1024 = 30MB

NOTE: If both values are set to zero in the registry, PagedPoolSize will calculate to approximately memory size)

The kernel debugger can be used to view these global variables in memory.
The values shown below are for a 32 MB x86-based computer running Windows NT 3.5, build 807:

kd> dd MmDefaultMaximumNonPagedPool
8019e4d4 00100000 (1Mbyte)

kd> dd MmSizeOfNonPagedPoolInBytes
80196188 00120000 (1,179,648)

kd> dd MmMinimumNonPagedPoolSize l1
8019e4cc 00040000 (262144)

kd> dd MmNumberOfPhysicalPages l1
801961ac 00002010 (8208)

kd> dd MmMinAdditionNonPagedPoolPerMb l1
8019e4d0 00008000 (32768)

kd> dd MmMaximumNonPagedPoolInBytes l1
80196310 00c20000 (12713984)

kd> dd MmSizeOfPagedPoolInBytes l1
8019e4dc 02000000 (33554432)

These values may be modified in the registry.

WARNING: Using the Registry Editor incorrectly can cause serious, system- wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of the Registry Editor can be solved. Use this tool at your own risk.

The page pooled memory management parameters are located in:


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

For additional information about the /3GB setting, click the article number below to view the article in the Microsoft Knowledge Base:

Q171793 Information on Application Use of 4GT RAM Tuning

Microsoft Windows 2000

The Windows 2000 memory model increases the amount of nonpaged pool and paged pool memory available to the system.

A Windows 2000-based 32-bit x86 computer that is booted without the /3GB switch is changed to a maximum paged pool of approximately 300-470 MB (from 192 MB in Windows NT 4.0).

With Windows 2000, the amount of nonpaged pool that the operating system can use is increased to 256 MB (from 128 MB in Windows NT 4.0).

If the server is booted with the /3GB switch enabled, the memory model remains that same for nonpaged and paged pool as in Windows NT 4.0.

Additional query words: server storage poolcalc pool non-paged

Keywords : kbnetwork ntnetserv NTSrvWkst
Version : WINDOWS:2000; winnt:3.5,3.51,4.0
Platform : WINDOWS winnt
Issue type :