How can you find the processor number a thread is running on?

Question

I have a memory heap manager which partitions the heap into different segments based on the number of processors on the system. Memory can only be allocated on the partitio

Answer 1

In addition to Antony Vennard's answer and the code on the cited site, here is code that will work for Visual C++ x64 as well (no inline assembler):

DWORD GetCurrentProcessorNumberXP() {
   int CPUInfo[4];   
   __cpuid(CPUInfo, 1);
   // CPUInfo[1] is EBX, bits 24-31 are APIC ID
   if ((CPUInfo[3] & (1 << 9)) == 0) return -1;  // no APIC on chip
   return (unsigned)CPUInfo[1] >> 24;
}

A short look at the implementation of GetCurrentProcessorNumber() on Win7 x64 shows that they use a different mechanism to get the processor number, but in my (few) tests the results were the same for my home-brewn and the official function.