IoGetDeviceNumaNode function (wdm.h)

Article
04/18/2022

The IoGetDeviceNumaNode routine gets the node number of a device.

Syntax

NTSTATUS IoGetDeviceNumaNode(
  [in]  PDEVICE_OBJECT Pdo,
  [out] PUSHORT        NodeNumber
);

Parameters

[in] Pdo

A pointer to a physical device object (PDO). This parameter points to a DEVICE_OBJECT structure that represents a physical device.

[out] NodeNumber

A pointer to a location into which the routine writes the node number, if the node number is known.

Return value

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

Return code	Description
STATUS_NOT_FOUND	The node number of this device is unknown.
STATUS_INVALID_PARAMETER	The Pdo parameter is NULL or does not point to a valid device object.

Remarks

In a non-uniform memory access (NUMA) multiprocessor architecture, a node is a collection of processors that share fast access to a region of memory. Memory access is non-uniform because a processor can access the memory in its node faster than it can access the memory in other nodes.

A device (for example, a network controller or storage controller) that is connected to a particular node can access the memory in this node faster than it can access the memory in other nodes. The Pdo parameter points to a PDO that represents the bus connection between the device and the node.

If a NUMA multiprocessor system contains n nodes, the nodes are numbered from 0 to n-1. To obtain the highest node number, call the KeQueryHighestNodeNumber routine.

After the system is initialized, the node count remains fixed while the system continues to run. This count might include memory-only nodes, which are nodes that contain memory but no active logical processors. A node in which all the logical processors are inactive is effectively a memory-only node until the first processor in the node starts to run. Do not assume that the node that a device is connected to contains active processors.

If a system does not have a NUMA architecture, the routine writes zero to the location that the NodeNumber parameter points to. An example of non-NUMA architecture is a symmetric multiprocessor system (SMP).

Requirements

Requirement	Value
Minimum supported client	Available in Windows 7 and later versions of the Windows operating systems.
Target Platform	Universal
Header	wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	PASSIVE_LEVEL
DDI compliance rules	HwStorPortProhibitedDDIs(storport), PowerIrpDDis(wdm)