C++ How to limit visual studios multi-processor compilation

Setting the "Maximum number of parallel project builds" is not the answer if you have a single C++ project with lots of .cpp files and you don't want 8 building at once. To control that, go to Tools > Options > Projects and Solutions > VC++ Project Settings, and in the Build section, set Maximum Concurrent C++ Compilations to the max number of .cpp files you want to compile in parallel. The default setting appears to be 0, which apparently means there is no maximum. I have 4 cores/8 threads, and set this value to 4, and VS now only compiles 4 files at a time instead of 8.

These instructions are based on Visual Studio 2017, but I think it's been this way for a few releases.

I found a workaround that actually works for me. Manually restrict affinity for VS process. Open Task Manager, go to Details tab, right click on devenv.exe, select "Set affinity". In the dialog untick several cores. That's it. All spawned cl.exe processes will inherit affinity, and thus won't run on unticked cores.

Also, go and cast your vote for a feature request for Visual Studio: https://developercommunity.visualstudio.com/content/idea/436208/limit-cpu-usage-of-visual-studio.html

A more optimal answer comes from Mikhail Virovets at https://developercommunity.visualstudio.com/comments/497084/view.html

Decrease the compiler process priority to below normal. This means it will use as much CPU as possible but without interfering with other things you're trying to use.

Define a registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\cl.exe\PerfOptions

Then create a DWORD value named CpuPriorityClass = 5 (5 means "below normal").

Note that this affects all processes named "cl.exe".