Multi-core CPU processors are common nowadays, including dual-core processors (e.g., Intel Core Duo), quad-core processors (e.g., Intel Core i5), and hexa-core processors (e.g., AMD Phenom II X6). Also, many server-grade physical machines are equipped with more than one CPU processor. In order to find the number CPUs, and the number of cores per CPU, you can refer to /proc/cpuinfo.
A sample /proc/cpuinfo of HP Proliant DL 380 G7 server is as follows. The HP Proliant server is equipped with two Intel Xeon 5600 series processors.
processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 44 model name : Intel(R) Xeon(R) CPU E5620 @ 2.40GHz stepping : 2 cpu MHz : 2399.316 cache size : 12288 KB physical id : 0 siblings : 8 core id : 0 cpu cores : 4 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 11 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr dca sse4_1 sse4_2 popcnt lahf_lm ida bogomips : 4802.28 clflush size : 64 cache_alignment : 64 address sizes : 40 bits physical, 48 bits virtual power management: . . . .
To find the number of physical CPUs:
To find the number of cores per CPU:
cpu cores : 4
The total number of processors available is the number of physical CPUs multiplied by the number of cores per CPU.
To find the total number of processors:
Note that Intel Xeon 5600 series processors have Intel Hyper-Threading capability. So each core shows up as "two" processors in Linux, and thus the total processor count seen by Linux is 16 (= 2 x 4 x 2).
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