Processor Information

This section describes functions and structures used to retrieve detailed information about the processors installed in the system.

Core Concepts

Understanding processor capabilities is crucial for optimizing application performance and ensuring compatibility. Windows provides a set of APIs that allow applications to query information such as the number of processors, cache sizes, clock speed, and feature sets.

Key Functions

`GetSystemInfo`

Retrieves information about the current system, including the processor architecture, level, revision, page size, and the number of active processors. This is a foundational function for obtaining basic system details.


BOOL GetSystemInfo(
  LPSYSTEM_INFO lpSystemInfo
);

The lpSystemInfo parameter points to a SYSTEM_INFO structure that receives the system information.

`GetLogicalProcessorInformation`

Retrieves extended system information, including processor affinity masks, cache topology, NUMA node information, and more. This function provides a more granular view compared to GetSystemInfo.


BOOL GetLogicalProcessorInformation(
  PSYSHLOGICALPROCESSORINFORMATION Buffer,
  PDWORD ReturnedLength
);

The Buffer parameter is a pointer to an array of SYSTEM_LOGICAL_PROCESSOR_INFORMATION structures. The ReturnedLength parameter specifies the size of the buffer.

Important Structures

`SYSTEM_INFO`

This structure contains information about the current computer. It includes details relevant to processors and the system in general.

Member	Description
`wProcessorArchitecture`	The architecture of the processor (e.g., x86, x64, ARM).
`dwPageSize`	The size of a page in memory, in bytes.
`lpMinimumApplicationAddress`	A pointer to the lowest memory address accessible to applications and DLLs.
`lpMaximumApplicationAddress`	A pointer to the highest memory address accessible to applications and DLLs.
`dwActiveProcessorMask`	A bitmask representing the set of active logical processors.
`dwNumberOfProcessors`	The number of logical processors available on the current system.
`dwProcessorType`	An obsolete member that indicates the processor type.
`dwAllocationGranularity`	The granularity of allocation, in bytes, that is used by the memory allocation functions.
`wProcessorLevel`	The Intel-compatible processor level.
`wProcessorRevision`	The Intel-compatible processor revision.

`SYSTEM_LOGICAL_PROCESSOR_INFORMATION`

This structure describes the logical processors in a system. It includes information about processor cores, NUMA nodes, and caches.

Member	Description
`ProcessorMask`	A `KAFFINITY` mask that specifies the processors in the group.
`Relationship`	A `LOGICAL_PROCESSOR_RELATIONSHIP` enumeration value that specifies the relationship between the processors.
`ProcessorCore.Flags`	A flag indicating whether the processor core is the PC-Portable type.
`ProcessorCore.NumSymmetricCores`	The number of symmetric cores in the group.
`Cache.Level`	The cache level (e.g., L1, L2, L3).
`Cache.Associativity`	The associativity of the cache.
`Cache.LineSize`	The cache line size, in bytes.
`Cache.Size`	The total size of the cache, in bytes.
`NumaNode.NodeNumber`	The NUMA node number.

Example Usage

The following C++ code snippet demonstrates how to use GetSystemInfo to retrieve basic processor information:


#include <windows.h>
#include <iostream>

int main() {
    SYSTEM_INFO sysInfo;
    GetSystemInfo(&sysInfo);

    std::wcout << L"Number of Processors: " << sysInfo.dwNumberOfProcessors << std::endl;
    std::wcout << L"Processor Architecture: " << sysInfo.wProcessorArchitecture << std::endl;
    std::wcout << L"Page Size: " << sysInfo.dwPageSize << L" bytes" << std::endl;

    return 0;
}

Note: The processor architecture values (e.g., PROCESSOR_ARCHITECTURE_INTEL, PROCESSOR_ARCHITECTURE_AMD64) are defined in winnt.h.

Important: For modern systems with multiple cores and hyperthreading, dwNumberOfProcessors typically reports the number of logical processors, not physical cores. Use GetLogicalProcessorInformation for more detailed topology.