Calculate Socket and Core Numbers

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To activate or deactivate a core using operating system commands, you must know the number or numbers of the virtual or logical processors associated with that core. This task provides instructions for calculating those numbers.

Your server has two, four, or eight sockets numbered 0 through 1, 3, or 7.
Each socket has 15 cores numbered 0 through 14.
Each core has one or two virtual processors associated with it, depending on whether hyperthreading is enabled or not. To deactivate a core, you must deactivate both virtual processors associated with that core.

You can also use operating system commands to display virtual processor numbers. See:

Calculate the number of the first virtual processor.
1. Multiply the socket number by 15.
2. Add the core number to the socket number.
For example, to calculate the number of the first virtual processor for core 2 on socket 2:

2 x 15 +2 = 32

Note - If hyperthreading is disabled, this is the only number you need to activate or deactivate the core.
If hyperthreading is enabled, calculate the number of the second virtual processor.
1. Calculate the number of the first virtual processor by using the number or the calculation from Step 1.
  For example: 2 x 15 +2 = 32
2. To calculate the total number of first virtual processors in the system, multiply the number of sockets by 15.
  For example, in an 8 socket system: 8 x 15 = 120
3. Add the number of the first virtual processor to the total number of first virtual processors in the system.
  For example: 120 + 32 = 152
To obtain the core number, divide the first virtual processor number by 15.
- The quotient is the socket number.
- The remainder is the core number.
For example 32 / 15 = 2 with a remainder of 2. Virtual processor 32 runs on socket 2, core 2.
Note - To calculate the remainder using a calculator:
1. Divide the core number by the number of processors per core. This produces a whole number and a decimal. For example:
  
  32 / 15 = 2.133333333333333
2. The whole number is the socket. Subtract it from the total. For example:
  
  2.133333333333333 - 2 = .133333333333333
3. Multiply the decimal by 15 to find the remainder, which is the core number on this socket. For example:
  
  .133333333333333 X 15 = 2.
Core 32 is processor 2, core 2.