Large-page support enables server applications to establish large-page memory regions, which is particularly useful on 64-bit Windows. Each large-page translation uses a single translation buffer inside the CPU. The size of this buffer is typically three orders of magnitude larger than the native page size; this increases the efficiency of the translation buffer, which can increase performance for frequently accessed memory.

To use large-page support, do the following:

1. Obtain the SeLockMemoryPrivilege privilege by calling the AdjustTokenPrivileges function. For more information, see Changing Privileges in a Token.
2. Retrieve the minimum large-page size by calling the GetLargePageMinimum function.
3. Include the MEM_LARGE_PAGES value when calling the VirtualAlloc function. The size and alignment must be a multiple of the large-page minimum.

The following are restrictions when using large pages:

• These memory regions may be difficult to obtain after the system has been running for a long time because the space for each large page must be contiguous, but the memory may have become fragmented. This is an expensive operation; therefore, applications should avoid making repeated large page allocations and allocate them all one time at startup instead.
• The memory is always read-write, fully cacheable, and nonpageable.
• The memory is part of the process private bytes but not part of the working set.
• Large-page allocations are not subject to job limits.
• WOW64 on Intel Itanium-based systems does not support 32-bit applications that use this feature. The applications should be recompiled as native 64-bit applications.

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Build date: 8/22/2008