Is clock_gettime() adequate for submicrosecond timing?

Question

I need a high-resolution timer for the embedded profiler in the Linux build of our application. Our profiler measures scopes as small as individual functions, so it needs a

Answer 1

I ran some benchmarks on my system which is a quad core E5645 Xeon supporting a constant TSC running kernel 3.2.54 and the results were:

clock_gettime(CLOCK_MONOTONIC_RAW)       100ns/call
clock_gettime(CLOCK_MONOTONIC)           25ns/call
clock_gettime(CLOCK_REALTIME)            25ns/call
clock_gettime(CLOCK_PROCESS_CPUTIME_ID)  400ns/call
rdtsc (implementation @DavidSchwarz)     600ns/call

So it looks like on a reasonably modern system the (accepted answer) rdtsc is the worst route to go down.