现在机器的cpu越来越复杂，一个cpu，经常是几个内核，4，6，8都不是什么稀罕的事情。
当年我公司购买一台8cpu的AMD服务器，双核，当时看到cpu很壮观，16个cpu。
现在一台普通的2U的服务器，都可能看到这种场景。
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"