CcScheduleReadAheadEx function (ntifs.h)
The CcScheduleReadAheadEx routine performs read-ahead (also called "lazy read") on a cached file. The I/O byte count for the operation is charged to the issuing thread.
Syntax
void CcScheduleReadAheadEx(
[in] PFILE_OBJECT FileObject,
[in] PLARGE_INTEGER FileOffset,
[in] ULONG Length,
[in] PETHREAD IoIssuerThread
);
Parameters
[in] FileObject
Pointer to a file object for the file on which read-ahead is to be performed.
[in] FileOffset
Pointer to a variable that specifies the starting byte offset within the cached file where the last read occurred.
[in] Length
Length in bytes of the range that was last read.
[in] IoIssuerThread
The thread issuing the read ahead request. For a file system with disk I/O accounting enabled, this is the thread the I/O is charged to. If IoIssuerThread is NULL, the I/O is charged to the current thread.
Return value
None
Remarks
CcScheduleReadAheadEx should be called only when Length >= 256. Measurements have shown that calling CcScheduleReadAheadEx for smaller reads actually decreases performance.
CcScheduleReadAheadEx can only be called after a successful call to CcCopyRead, CcCopyReadEx, CcFastCopyRead, or CcMdlRead.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows 8 |
| Target Platform | Universal |
| Header | ntifs.h (include Ntifs.h, FltKernel.h) |
| Library | NtosKrnl.lib |
| DLL | NtosKrnl.exe |
| IRQL | <= APC_LEVEL |