Set tun.avoid_cpus to a list of logical CPUs to remove from the affinity of
every thread of the process on Linux, before services start and reader CPUs
are chosen. Later threads inherit the restricted mask; enumeration repeats so
threads created meanwhile are covered. Inherited taskset and cgroup
restrictions are kept. Keeping Nebula off the underlay NIC's receive IRQ CPUs
and their SMT siblings is what this is for; the example configuration shows
how to find them.
Invalid IDs, a list that would leave a thread no CPU, and syscall failures
fail startup. Configuration tests only validate. Other platforms log and
ignore the setting. The exclusion is process-wide, including embedded use, and
not reloadable. It is independent of thread pinning.
New API: util.AvoidCPUs, next to the existing PinThreadToCPU and AllowedCPUs.
Tests run in a child process and check existing and new threads, preserved
inherited masks, validation without changes, and the unix.CPUSet bounds on
32- and 64-bit platforms. No isolated performance claim is made.
The goroutines Main starts stop only when its context does, and only a caller
holding the Control can arrange that. Cancelling solely on error left a config
test, which returns no Control and no error, with the lighthouse query worker
and a hostname resolver per dns named static host running for the life of the
process. Every embedder that validates a config in process rather than by
exec'ing pays for that on each config load, dnclient and the apple clients
included.
Co-authored-by: Nate Brown <nbrown.us@gmail.com>
Ryan Huber