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Memory Management Registry Keys

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System virtual address (VA) space on 32-bit systems can become exhausted due to fragmentation. Several registry keys can be used to configure memory limits on 32-bit systems that experience this issue. System VA space on 64-bit systems is not subject to exhaustion by fragmentation; therefore, these keys have no effect on 64-bit systems.

For 32-bit systems, these memory management registry keys must be explicitly created under the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\Current Control Set\Control\Session Manager\Memory Management

Windows Server 2008 and Windows Vista: These registry keys are available on 32-bit systems starting with Windows Server 2008 and Windows Vista with Service Pack 1 (SP1).

For default memory and address space limits on both 32-bit and 64-bit systems, see Memory Limits for Windows Releases.

The following table describes the memory management registry keys that can be used to configure memory limits on 32-bit systems. All of these keys have a REG_DWORD type and possible values that range from 0 through 2,048 MB. The default is 0, which means no limit is enforced. Values are automatically rounded up to the next system VA allocation boundary, which is 2 MB on 32-bit systems that have Physical Address Extension (PAE) enabled and 4 MB on 32-bit systems that do not have PAE enabled.

Key Description
NonPagedPoolLimit Specifies the maximum amount of system VA space that can be used by the nonpaged pool. Under certain conditions, this limit may be exceeded by a small amount.
PagedPoolLimit Specifies the maximum amount of system VA space that can be used by the paged pool.
SessionSpaceLimit Specifies the maximum amount of system VA space that can be used by session space allocations.
SystemCacheLimit Specifies the maximum amount of system VA space that can be used by the system cache. Under certain conditions, this limit may be exceeded by a small amount.
SystemPtesLimit Specifies the maximum amount of system VA space that can be used by I/O mappings and other resources that consume system page table entries (PTEs).

 

Determining whether system VA space is being exhausted requires the use of a kernel debugger. For more information, see Debugging Tools for Windows.