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

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

Additional query words: server storage poolcalc pool non-paged


Keywords          : kbnetwork ntnetserv NTSrvWkst 
Version           : WinNT:3.5,3.51,4.0
Platform          : winnt 
Issue type        :

Last Reviewed: February 24, 1999