Nodejs os.cpu return not allowed cpu

The os.cpus() API added in Nodejs v0.3.3 shows all processors in /proc/cpuinfo. This API is often used to give a suggestion of how many worker processes created by cluster. However, in a docker/lxc environment, some
of the cpus are not allowed to be used by a container.
For more accurate information, we should cat /proc/self/status. This file will show the specific allowed cpus. Or use the command nproc.