NdisSystemActiveProcessorCount function (ndis.h)

Article
04/01/2021

The NdisSystemActiveProcessorCount function returns the number of currently active processors in the local computer.

Syntax

ULONG NdisSystemActiveProcessorCount(
  PKAFFINITY ActiveProcessors
);

Parameters

ActiveProcessors

A pointer to a KAFFINITY-typed variable that receives a bitmap that represents the set of currently active processors. In a hot-add environment, this bitmap can change during runtime.

Return value

NdisSystemActiveProcessorCount returns the number of currently active processors in the local computer.

Remarks

An NDIS driver might call the NdisSystemActiveProcessorCount function during initialization before it allocates resources.

NdisSystemActiveProcessorCount is similar to the KeQueryActiveProcessorCount function.

Note NDIS drivers should not use NdisSystemProcessorCount to retrieve the number of currently active processors,

Note NdisSystemActiveProcessorCount might not map processors to the bits in the returned [**KAFFINITY**](/windows-hardware/drivers/kernel/interrupt-affinity-and-priority#about-kaffinity) value consecutively. and NdisSystemActiveProcessorCount might not return the same bitmap every time that it is called.

The value that NdisSystemActiveProcessorCount returns can change at runtime on SKUs that support hot-add CPU functionality.

The Windows Server 2008 Enterprise operating system and the Windows Server 2008 Datacenter operating system support dynamic hardware partitioning. As part of dynamic hardware partitioning, Windows Server 2008 supports hot-add operations for CPUs at runtime. In a hot-add CPU environment, the number of processors might not remain constant during runtime.

Requirements

Requirement	Value
Minimum supported client	Supported in NDIS 6.1. For NDIS 6.20 and later, use NdisGroupActiveProcessorCount instead.
Target Platform	Universal
Header	ndis.h (include Ndis.h)
Library	Ndis.lib
IRQL	Any level