Well, that depends. CLOCK_MONOTONIC_RAW does avoid NTP slewing, but NTP doesn't just adjust the time scale to adjust for offsets - it also attempts to correct for frequency error in your system clock itself. If you use CLOCK_MONOTONIC_RAW, you don't get that correction; you get something that on desktop hardware can easily be tens of ppm off from actual time. Of course, your MONOTONIC_RAW clock is still subject to the vagaries of physics; as temperature or system load changes, depending on the quality of your time source, you might get significant changes in the rate of CLOCK_MONOTONIC_RAW as well (which NTP will correct for in CLOCK_MONOTONIC, given enough time to adjust).