現在機器的cpu越來越復雜，一個cpu，經常是幾個內核，4，6，8都不是什麼稀罕的事情。
當年我公司購買一台8cpu的AMD服務器，雙核，當時看到cpu很壯觀，16個cpu。
現在一台普通的2U的服務器，都可能看到這種場景。
http://planet.admon.org/howto/about-cpu-the-logical-and-physical-cores/
There are some commands here to help identify these type of information quickly on a running Linux:
Total amount of processors including the logical ones:
# cat /proc/cpuinfo | grep "processor"| wc -l
Total amount of CPU package:
# cat /proc/cpuinfo | grep "physical id" | sort | uniq | wc -l
How many cores for each CPU. (Here we should call CPU as physical package as we mentioned above):
# cat /proc/cpuinfo | grep "cpu cores" | wc -l
For each physical CPU, the amount of Logical CPU (the logical CPU can be physical cores, soft cores like threaded, or both).
# cat /proc/cpuinfo | grep "siblings"