KeGetProcessorNumberFromIndex function (ntifs.h)

Article
11/04/2022

The KeGetProcessorNumberFromIndex routine converts a systemwide processor index to a group number and a group-relative processor number.

Syntax

NTSTATUS KeGetProcessorNumberFromIndex(
  [in]  ULONG             ProcIndex,
  [out] PPROCESSOR_NUMBER ProcNumber
);

Parameters

[in] ProcIndex

A systemwide processor index. If a multiprocessor system contains a total of n logical processors, valid processor indexes range from 0 to n-1.

[out] ProcNumber

A pointer to a caller-allocated PROCESSOR_NUMBER structure into which the routine writes the group number and group-relative processor number of the processor that is identified by ProcIndex.

Return value

KeGetProcessorNumberFromIndex returns STATUS_SUCCESS if the call is successful. Possible error return values include the following:

Return code	Description
STATUS_INVALID_PARAMETER	The ProcIndex parameter value is not a valid processor index.

Remarks

This routine accepts as input a processor index that identifies the processor across the entire multiprocessor system. The output value is a PROCESSOR_NUMBER structure that identifies a processor by its group number and its processor number within the group.

For example, if a multiprocessor system contains two groups, and each group contains 64 logical processors, the processor numbers in each group range from 0 to 63, but the systemwide processor indexes range from 0 to 127.

To obtain the total number of active logical processors in the system, call the KeQueryActiveProcessorCountEx routine.

The KeGetProcessorIndexFromNumber routine converts a group number and a group-relative processor number to a systemwide processor index.

Examples

The following code example uses the KeQueryActiveProcessorCountEx and KeGetProcessorNumberFromIndex routines to enumerate all active logical processors in the system:

ULONG Count;
ULONG ProcIndex;
PROCESSOR_NUMBER ProcNumber;

Count = KeQueryActiveProcessorCountEx(ALL_PROCESSOR_GROUPS);
for (ProcIndex = 0; ProcIndex < Count; ProcIndex += 1)
{
    KeGetProcessorNumberFromIndex(ProcIndex, &ProcNumber);

    // Do something with the contents of ProcNumber.
    ...
}

The constant value ALL_PROCESSOR_GROUPS is defined in Winnt.h and Ntdef.h.

Requirements

Requirement	Value
Minimum supported client	Windows 7
Target Platform	Universal
Header	ntifs.h (include Ntddk.h, Wdm.h, Ntddk.h, Ntifs.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	Any level

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