Comment by madog

Just use gettimeofday/clock_gettime via vDSO.

  struct timespec ts;
  clock_gettime(CLOCK_MONOTONIC, &ts);

On arm64 it directly uses the cntvct_el0 register under the hood but with a standard/easy to use API instead of messing about with inline assembly. Also avoids a context switch because it's vDSO.