[sunfmin]

Thanks, but there will be I/O waiting stuff right? For that whois command example, I find the CPU usage is zero if I am not running it parallel.

[drtse4]

Yup, if your jobs are i/o heavy the cpu time is wasted waiting if you execute them in a strictly sequential way. With your worker pool the cpu intensive part of the jobs is instead being executed concurrently GOMAXPROCS jobs at a time.