MEMORY_CACHING_TYPE enumeration

The MEMORY_CACHING_TYPE enumeration type specifies the permitted caching behavior when allocating or mapping memory.

Syntax


typedef enum _MEMORY_CACHING_TYPE { 
  MmNonCached               = 0,
  MmCached                  = 1,
  MmWriteCombined           = 2,
  MmHardwareCoherentCached  = 3,
  MmNonCachedUnordered      = 4,
  MmUSWCCached              = 5,
  MmMaximumCacheType        = 6
} MEMORY_CACHING_TYPE;

Constants

MmNonCached

The requested memory should not be cached by the processor.

MmCached

The processor should cache the requested memory.

MmWriteCombined

The requested memory should not be cached by the processor, but writes to the memory can be combined by the processor.

MmHardwareCoherentCached

Reserved for system use.

MmNonCachedUnordered

Reserved for system use.

MmUSWCCached

Reserved for system use.

MmMaximumCacheType

Reserved for system use.

Remarks

Processor translation buffers cache virtual to physical address translations. These translation buffers allow many virtual addresses to map a single physical address. However, only one caching behavior is allowed for any given physical address translation. Therefore, if a driver maps two different virtual address ranges to the same physical address, it must ensure that it specifies the same caching behavior for both. Otherwise, the processor behavior is undefined with unpredictable system results.

Requirements

Version

Supported in Windows 2000 and later versions of Windows.

Header

Wdm.h (include Ntddk.h or Wdm.h)

See also

MmAllocateContiguousMemorySpecifyCache
MmFreeContiguousMemorySpecifyCache
MmMapIoSpace
MmMapLockedPagesSpecifyCache
MmMapLockedPagesWithReservedMapping

 

 

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