openjdk7-hotspot os.hpp
//Linux版(jdk7/hotspot/src/os/linux/vm/os_linux.cpp)
// System loadavg support.  Returns -1 if load average cannot be obtained.
// Linux doesn't yet have a (official) notion of processor sets,
// so just return the system wide load average.
int os::loadavg(double loadavg[], int nelem) {
  return ::getloadavg(loadavg, nelem);
}