首先，看看什么是超线程概念
超线程技术就是利用特殊的硬件指令，把两个逻辑内核模拟成两个物理芯片，让单个处理器都能使用线程级并行计算，进而兼容多线程操作系统和软件，减少了CPU的闲置时间，提高的CPU的运行效率。
超线程技术是在一颗CPU同时执行多个程序而共同分享一颗CPU内的资源，理论上要像两颗CPU一样在同一时间执行两个线程，虽然采用超线程技术能同时执行两个线程，但它并不象两个真正的CPU那样，每个CPU都具有独立的资源。当两个线程都同时需要某一个资源时，其中一个要暂时停止，并让出资源，直到这些资源闲置后才能继续。因此超线程的性能并不等于两颗CPU的性能。
其次，看看物理CPU个数，核数以及线程数的关系
总核数 = 物理CPU个数 * 每颗物理CPU的核数
总逻辑CPU数 = 物理CPU个数 * 每颗物理CPU的核数 * 超线程数
上述公式中，逻辑CPU数即线程数
如何查看CPU物理个数
# grep 'physical id' /proc/cpuinfo | sort -u
physical id : 0
physical id : 1
如何查看每个物理CPU的核数
# grep 'core id' /proc/cpuinfo | sort -u | wc -l
8
如何查看总的逻辑CPU个数
# grep 'processor' /proc/cpuinfo | sort -u | wc -l
32
32/8/2=2，可见该CPU支持并已打开超线程。
如何查看CPU的型号
# dmidecode -s processor-version
Intel(R) Xeon(R) CPU E5-2658 @ 2.10GHz
Intel(R) Xeon(R) CPU E5-2658 @ 2.10GHz
关于物理CPU，核数以及超线程的区别
A core is the most basic computational unit of a processor. A processor is made up of one or more cores. Tradition processors had only one core while modern processors have multiple cores.
A core consists of an ALU, CU, and a set of registers.
A core consists of two levels of caches called L1 and L2 which is there in each core.
A processor consists of a cache that is shared by call cores called L3 cache. It is common to all cores.
A processor depending on the architecture can consist of a memory controller and an input/output controller.
Certain processor packages consist of Graphics Processing Units (GPU) as well.
A core that does not have hyper-threading can execute only one instruction at a time while a multicore processor made up of several cores can execute several instructions parallel. If a processor is made up of 4 cores that do not support hyper threading then that processor can execute 4 instructions at the same time.
A core having hyper-threading technology has redundant functional units so that they can execute multiple instructions at a time. For example, a core with 2 threads can execute 2 instructions at the same time hence a processor with 4 such cores can execute 2×4 instructions parallel. These threads are usually called logical cores and the task manager of Windows generally show the number of logical cores but not the physical cores.
