MEMORY_CACHING_TYPE enumeration (wdm.h)

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

Syntax

typedef enum _MEMORY_CACHING_TYPE {
  MmNonCached,
  MmCached,
  MmWriteCombined,
  MmHardwareCoherentCached,
  MmNonCachedUnordered,
  MmUSWCCached,
  MmMaximumCacheType,
  MmNotMapped
} 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.
MmNotMapped

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

Requirement	Value
Minimum supported client	Supported in Windows 2000 and later versions of Windows.
Header	wdm.h (include Ntddk.h, Wdm.h, Miniport.h, Wudfwdm.h)

See also

MmAllocateContiguousMemorySpecifyCache

MmFreeContiguousMemorySpecifyCache

MmMapIoSpace

MmMapLockedPagesSpecifyCache

MmMapLockedPagesWithReservedMapping