Feb. 21, 2012
10:49 p.m.
The original reason was that the Unix wall clock was more accurate than its CPU clock. If that's changed we should probably (perhaps in a platform-dependent way) change the default to the most accurate clock available.
Currently it seems clock_gettime() APIs have nanosecond resolution and OTOH gettimeofday() have microsecond. Other than that, clock_gettime() has a significant advantage: it has per-process timer available which will increase the accuracy of the timing information of the profiled application. -- Sumer Cip