Home/ Questions/Q 1032497
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-16T14:05:08+00:00

Any help figuring out how to do this would be great: How much time

  • 0

Any help figuring out how to do this would be great: How much time each CPU core spent in the C0 power state over the past second.

This is for a mac app so Objective-C, cocoa and c are needed.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    OS X doesn’t have any APIs that expose the c-state of the CPU. However, it seems like you can do this using the MWAIT/MONITOR instructions on intel CPUs. Intel mentions that you can track C-state residency using this technique in section 14.4 of the reference manual:

    Software should use CPUID to discover if a target processor supports the enumeration of MWAIT extensions. If CPUID.05H.ECX[Bit 0] = 1, the target processor supports MWAIT extensions and their enumeration (see Chapter 3, “Instruction Set Reference, A-M,” of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A).

    If CPUID.05H.ECX[Bit 1] = 1, the target processor supports using interrupts as break-events for MWAIT, even when interrupts are disabled. Use this feature to measure C-state residency as follows:

  2. Software can write to bit 0 in the MWAIT Extensions register (ECX) when issuing an MWAIT to enter into a processor-specific C-state or sub C-state.
  3. When a processor comes out of an inactive C-state or sub C-state, software can read a timestamp before an interrupt service routine (ISR) is potentially executed.

    4. You can find more info about the MWAIT instruction in the same manual. Good luck!

    Intel’s Reference Manual

    • 0