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DISK_CACHE_INFORMATION structure

The DISK_CACHE_INFORMATION structure is used with the IOCTL_DISK_GET_CACHE_INFORMATION request to retrieve cache information.

Syntax


typedef struct _DISK_CACHE_INFORMATION {
  BOOLEAN                       ParametersSavable;
  BOOLEAN                       ReadCacheEnabled;
  BOOLEAN                       WriteCacheEnabled;
  DISK_CACHE_RETENTION_PRIORITY ReadRetentionPriority;
  DISK_CACHE_RETENTION_PRIORITY WriteRetentionPriority;
  USHORT                        DisablePrefetchTransferLength;
  BOOLEAN                       PrefetchScalar;
  union {
    struct {
      USHORT Minimum;
      USHORT Maximum;
      USHORT MaximumBlocks;
    } ScalarPrefetch;
    struct {
      USHORT Minimum;
      USHORT Maximum;
    } BlockPrefetch;
  };
} DISK_CACHE_INFORMATION, *PDISK_CACHE_INFORMATION;

Members

ParametersSavable

Indicates, when set to 1, that the device is capable of saving any parameters in nonvolatile storage.

ReadCacheEnabled

Indicates, when set to 1, that the read cache is enabled.

WriteCacheEnabled

Indicates, when set to 1, that the write cache is enabled.

ReadRetentionPriority

Determines the likelihood of various types of data remaining in the cache. By means of this value, for instance, data cached from a READ or WRITE operation might be given a different priority than data cached under other circumstances, such as prefetch operations. Thus a value of EqualPriority indicates that no data is held in the cache on a preferential basis. When ReadRetentionPriority is set to EqualPriority, all types of data have equal access to cache memory. On the other hand, a value of KeepPrefetchedData indicates that a preference is to be given to prefetched data while a value of KeepReadData indicates that a preference is to be given to data cached from a READ operation. For more information about the values that can be assigned to this member see the DISK_CACHE_RETENTION_PRIORITY enumeration.

WriteRetentionPriority

See discussion under ReadRetentionPriority.

DisablePrefetchTransferLength

Disables prefetching. Prefetching might be disabled whenever the number of blocks requested exceeds the value in DisablePrefetchTransferLength. When zero, prefetching is disabled no matter what the size of the block request.

PrefetchScalar

When TRUE, Indicates that ScalarPrefetch.Maximum should be used together with the transfer length to calculate the amount of data that can be prefetched. When FALSE, BlockPrefetch.Maximum will be the maximum number of disk blocks that can be prefetched.

ScalarPrefetch
Minimum

Contains the scalar multiplier of the transfer length of the request when PrefetchScalar is TRUE. If PrefetchScalar is TRUE, the value in ScalarPrefetch.Minimum is multiplied by the transfer length to obtain the minimum amount of data that can be prefetched into the cache on a disk operation.

Maximum

Contains the scalar multiplier of the transfer length of the request when PrefetchScalar is TRUE. If PrefetchScalar is TRUE, the value in ScalarPrefetch.Maximum is multiplied by the transfer length to obtain the maximum amount of data that can be prefetched into the cache on a disk operation.

MaximumBlocks

Contains the maximum size, in blocks, of the transfer length.

BlockPrefetch
Minimum

Contains the scalar multiplier of the transfer length of the request when PrefetchScalar is TRUE. If PrefetchScalar is TRUE, the value in ScalarPrefetch.Minimum is multiplied by the transfer length to obtain the minimum amount of data that can be prefetched into the cache on a disk operation.

Maximum

Contains the scalar multiplier of the transfer length of the request when PrefetchScalar is TRUE. If PrefetchScalar is TRUE, the value in ScalarPrefetch.Maximum is multiplied by the transfer length to obtain the maximum amount of data that can be prefetched into the cache on a disk operation.

Requirements

Header

Ntdddisk.h (include Ntdddisk.h)

See also

IOCTL_DISK_GET_CACHE_INFORMATION
DISK_CACHE_INFORMATION

 

 

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