Microsoft KB Archive/121965

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HOWTO: Change Max Memory Allowed with MmProbeAndLockPages

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Q121965

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The information in this article applies to:


 * Microsoft Win32 Device Driver Kit (DDK) for Windows NT, versions 3.1, 3.5, 3.51

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SUMMARY
When using MmProbeAndLockPages, you need to remember that there is a limit to the amount of memory that can be locked down by MmProbeAndLockPages. The amount of memory is normally determined by the computer system at boot time. However, if you need to probe and lock more memory than is being allowed, there is a registry parameter that you can configure to allow you to determine the amount of memory available to probe and lock.

A key named IoPageLockLimit is located in HKEY_LOCAL_MACHINE\CurrentControlSet\Control\Session Manager\Memory Management. By default, this limit is 0, which indicates to the system that it should use a built-in algorithm to determine the amount of memory. You can change this value to indicate the number of bytes that can be used for MmProbeAndLockPages.

NOTE: Be careful when changing this value. The default value computed by the system when IoPageLockLimit is 0 is tuned specifically for system performance. Allowing the system to lock down more memory can have a detrimental effect on system performance.

Additional query words: NT DDK kernel mode memory

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Issue type : kbhowto

Technology : kbAudDeveloper kbWinDDKSearch kbWin32sSearch kbWin32DDKSearch kbWin32DDKNT310 kbWin32DDKNT350 kbWin32DDKNT351 kbWin32DDKNTSearch