Description from Brandon Mitchell @ Twitter:
"os::javaTimeNanos() shows hot on CPU_CLK_UNHALTED profiles due to
unnecessary function setup/teardown code around
Linux::supports_monotonic_clock(). I've added an inline annotation to
simplify the funcall to a NULL check, and verified the change using
both gdb disas and additional profiling. I observed a 2-3% CPU time
delta in my profile data for os::javaTimeNanos()."