![]() The XNU Kernel defines a funky little method called mp_rendevous(.). Its own right, but not what I’m after here. Just a mechanism logically grouping or separating threads, powerful in However, on Mac OS X actual thread affinity is not supported On Linux this is reasonably simple, you count the number ofĬPUs then iterate through all of them and use the pthread_setaffinity_np(.) to specify specify which CPU to run the CPUID instructions on. I need this code to run all of the CPUs on my Threads into a hierarchy of cores and sockets. This gets me most of the way there, I can group all of my ![]() References, but values that indicate threads have have the same id share Indicates that the hardware thread indicated by APIC 33 has the core id Shift: 5, Count: 8, Level Id: 1, Level Type: 2, x2APIC: 33, Group: 1 Shift: 1, Count: 2, Level Id: 0, Level Type: 1, x2APIC: 33, Group: 16 For example on my using the following code on my workstation (2 sockets, 8 cores, 16 threads): This is done by shifting the x2APIC ID right by the value specified by Shift. The Shift value is used to group x2APIC ID values into units at the next logical level. The x2APIC ID is a unique identifier for the smallest logic unit in the CPU. Than 2 are reserved, presumably for later use. ![]() Thread (1) or a physical core (2) or invalid (0). The ‘Level type’ describes whether the current level is a CPU | Level type | Reserved |Įxtended topology enumeration leaf is one of the CPUID indexes thatĪlso makes use of ECX as an input parameter. Process at this level | Reserved |ĮCX | Level No. ![]() The particular CPUID reference that provides information needed to building the topology is 0xB (11) – the extended topology enumeration leaf. The 3rd andįinal section are the input parameters. Refers to the 2nd letter of the register designation. The snippet "=a" (data) means store the result in the EAX register in the variable data. The second line defines the output parameters. An inline asm segment consists of 3 parts. The ones used for the CPUID instruction are EAX,ĮBX, ECX, and EDX (referenced as RAX, RBX, etc if using 64 bit Those unfamiliar with Intel inline assembly, the Intel CPU defines a On my Mac I get the following: // Output: The code shows how to get the vendor string from the CPU. Instruction we need a little bit of inline assembler. hyperthreading) to sizes of the various levels ![]() There is a raft of information available from listing of the CPUįeatures available (e.g. The is the primary mechanism for getting information about the CPU. Intel exposes an instruction called CPUID. The first step was to understand what information was available from the CPU. Not only did it require getting down and dirty with a bit ofĬ++ and X86 Assembly, it also required writing a MacOS kernel extension. This sounds very simple, it’s actually fraught with a number of little To map the operating system’s processors to hardware threads, then buildĪ picture of which cores and sockets those threads reside. Needed to build a topology of the CPUs on a given system. The capabilities of Linux’s /proc/cpuinfo on Mac OS. Within a project I’ve been working on I’ve had the need to simulate ![]()
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