search for: clock_getcpuclockid

...ses of rdtsc, I found that glibc has its own implementation of clock_gettime that uses rdtsc directly! The manpage for clock_gettime ("man 3 clock_gettime") has a lengthy caveat about using clock_gettime on an SMP system BUT provides a mechanism to test to see if your SMP system is safe, clock_getcpuclockid(0). See for example (near the end): http://linux.die.net/man/3/clock_gettime But testing this on a system I know is unsafe, the test says my system is safe! Looking at the source code, I can see why... the test is a compile-time test, not a run-time test, and on x86 it appears that it will alway...