Intel 64 and IA-32 Architectures Software Developers Manual Volume 3A, System Programming Guide, Part 1

Vol. 3A 7-45
MULTIPLE-PROCESSOR MANAGEMENT
Example 7-3. Compute the Number of Packages, Cores, and Processor Relationships in a MP
System
a) Assemble lists of PACKAGE_ID, CORE_ID, and SMT_ID of each enabled logical processors
//The BIOS and/or OS may limit the number of logical processors available to applications
// after system boot. The below algorithm will compute topology for the processors visible
// to the thread that is computing it.
// Extract the 3-levels of IDs on every processor
// SystemAffinity is a bitmask of all the processors started by the OS. Use OS specific APIs to
// obtain it.
// ThreadAffinityMask is used to affinitize the topology enumeration thread to each processor
using OS specific APIs.
// Allocate per processor arrays to store the Package_ID, Core_ID and SMT_ID for every started
// processor.
ThreadAffinityMask = 1;
ProcessorNum = 0;
while (ThreadAffinityMask != 0 && ThreadAffinityMask <= SystemAffinity) {
// Check to make sure we can utilize this processor first.
if (ThreadAffinityMask & SystemAffinity){
Set thread to run on the processor specified in ThreadAffinityMask
Wait if necessary and ensure thread is running on specified processor
InitAPIC_ID = GetInitAPIC_ID();
Extract the Package, Core and SMT ID as explained in three level extraction
algorithm
PackageID[ProcessorNUM] = PACKAGE_ID;
CoreID[ProcessorNum] = CORE_ID;
SmtID[ProcessorNum] = SMT_ID;
ProcessorNum++;
}
ThreadAffinityMask <<= 1;
}
NumStartedLPs = ProcessorNum;
b) Using the list of PACKAGE_ID to count the number of physical packages in a MP system and
construct, for each package, a multi-bit mask corresponding to those logical processors residing in
the same package.
// Compute the number of packages by counting the number of processors
// with unique PACKAGE_IDs in the PackageID array.
// Compute the mask of processors in each package.