Provide APIs for CPU isolation (benchmarks)

[giampaolo]

Benchmarking is a complex science, see: https://easyperf.net/blog/2019/08/02/Perf-measurement-environment-on-Linux.
It seems like an important aspect of benchmarking is asking the kernel to isolate a certain CPU, so that only a benchmark script can use it and avoid sharing that CPU with other processes.

It must be noted that psutil already provides some tools which one typically wants to run before a benchmark:

def set_highest_priority():
    """Set highest CPU and I/O priority (requires root)."""
    p = psutil.Process()
    if psutil.WINDOWS:
        p.nice(psutil.HIGH_PRIORITY_CLASS)
    else:
        p.nice(-20)

    if psutil.LINUX:
        p.ionice(psutil.IOPRIO_CLASS_RT, value=7)
    elif psutil.WINDOWS:
        p.ionice(psutil.IOPRIO_HIGH)

It would be nice if the above code could be extended to allow something like this:

>>> psutil.cpu_isolation()  # get
[]
>>> psutil.cpu_isolation([1, 2])  # set
>>> psutil.cpu_isolation()
[1, 2]
>>>
>>> psutil.Process().cpu_affinity([1, 2])  # isolate this process
>>>

Useful URLs

• get() on Linux: https://github.com/psf/pyperf/blob/db186b120a1b3abcb0a5ffc25585fa828c823566/pyperf/_cpu_utils.py
• cset CLI command source code: https://github.com/lpechacek/cpuset