SetProcessAffinityMask
Syntax
#include <windows.h>
BOOL SetProcessAffinityMask(
HANDLE hProcess,
DWORD_PTR dwProcessAffinityMask
);Description
Sets a processor affinity mask for the specified process. The affinity mask determines the processors that the threads of the process are allowed to run on.
Parameters
| Parameter | Type | Description |
|---|---|---|
hProcess |
HANDLE | Handle to the process whose affinity mask is to be set. The handle must have the PROCESS_SET_INFORMATION access right. |
dwProcessAffinityMask |
DWORD_PTR | Bit mask that specifies the processors that the process's threads are allowed to run on. Each bit set to 1 represents a logical processor that is allowed. |
Return value
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
Remarks
- The affinity mask must be a subset of the system affinity mask retrieved via
GetProcessAffinityMask. - Setting an affinity mask that excludes all available processors results in failure.
- Affinity changes affect all existing threads in the process.
- When a process has multiple threads, each thread can also have its own affinity mask using
SetThreadAffinityMask.
Example
#include <windows.h>
#include <stdio.h>
int main(void)
{
HANDLE hProcess = GetCurrentProcess();
DWORD_PTR mask = 0x00000003; // Use CPU 0 and 1
if (!SetProcessAffinityMask(hProcess, mask)) {
printf("SetProcessAffinityMask failed. Error: %lu\n", GetLastError());
return 1;
}
printf("Affinity mask set to 0x%llx\n", (unsigned long long)mask);
return 0;
}