Change affinity of process with windows script

Question

In Windows, with

 START /node 1 /affinity ff cmd /C "app.exe"

I can set the affinity of app.exe (number of cores used by app.exe).

With a windows script, How I can change the affinity of a running process ?

Answer 1

PowerShell can do this task for you.

Get Affinity

$Process = Get-Process app
$Process | Select-Object ProcessorAffinity

Set Affinity

$Process = Get-Process app
$Process.ProcessorAffinity = 255

Example _{^{( 8 Core Processor )}}

Core #	Value	BitMask
Core 1	1	0x00000001
Core 2	2	0x00000010
Core 3	4	0x00000100
Core 4	8	0x00001000
Core 5	16	0x00010000
Core 6	32	0x00100000
Core 7	64	0x01000000
Core 8	128	0x10000000

Just add the decimal values together for which core you want to use.

• All 8 Cores = Value: 255 = BitMask: 0x11111111

Using with cmd.exe

You can use the PowerShell code from within the cmd shell by calling the PowerShell process with the code as an argument. Separate commands with a semi-colon.

> powershell.exe "Get-Process notepad++ | Select-Object ProcessorAffinity"

                                                         ProcessorAffinity
                                                         -----------------
                                                                       255


> powershell.exe "$p = Get-Process notepad++; $p.ProcessorAffinity = 13"

> powershell.exe "Get-Process notepad++ | Select-Object ProcessorAffinity"

                                                         ProcessorAffinity
                                                         -----------------
                                                                        13

Source

Here is a nicely detailed post on how to change a process's affinity:

Setting Processor Affinity @ EnergizedTech
archive.today / archive.org
^{_{(the broken images weren't important)}}

Answer 2

The accepted answer works, but only for the first process in the list. The solution to that in the comments does not work for me.

To change affinity of all processes with the same name use this:

Powershell "ForEach($PROCESS in GET-PROCESS processname) { $PROCESS.ProcessorAffinity=255}"

Where 255 is the mask as given in the accepted answer.

Answer 3

For anyone else looking for answers to this and not finding any, the solution I found was to use an app called WinAFC (or AffinityChanger). This is a partial GUI, partial command line app that allows you to specify profiles for certain executables, and will poll the process list for them. If it finds matching processes, it will change the affinity of those processes according to the settings in the loaded profile.

There is some documentation here: http://affinitychanger.sourceforge.net/

For my purposes, I created a profile that looked like this:

TestMode = 0
TimeInterval = 1
*\convert.exe := PAIR0+PAIR1

This profile sets any convert.exe process to use the first two CPU core pairs (CPU0, CPU1, CPU2, and CPU3), polling every second. TestMode is a toggle that allows you to see if your profile is working without actually setting affinities.

Hope someone finds this useful!

Answer 4

If you really like enums, you can do it this way. ProcessorAffinity is an IntPtr, so it takes a little extra type casting.

[flags()] Enum Cores {
  Core1 = 0x0001
  Core2 = 0x0002
  Core3 = 0x0004
  Core4 = 0x0008
  Core5 = 0x0010
  Core6 = 0x0020
  Core7 = 0x0040
  Core8 = 0x0080
}

$a = get-process notepad

[cores][int]$a.Processoraffinity
Core1, Core2, Core3, Core4

$a.ProcessorAffinity = [int][cores]'core1,core2,core3,core4'