How to limit the number of parallel cl.exe process

Question

I've recently noticed that once I start building the Visual Studio solution I'm working with (~200 C++ projects), I get a very large number of cl.exe processes.

I'm not surprised by the fact of several cl.exe running in parallel, because my projects are set up with /MP option.

But I would expect that their number would be limited by the following setting in the Visual Studio "Options".

I presume that running tens of processes in parallel on the 4-core PC is not the most efficient way to build the solution.

So, basically I've got two questions:

• Why do I observe such behavior?
• Is it possible to limit the number of cl.exe instances?

P.S. I normally compile my solution with Visual Studio 2013 Update 4, but the same behavior can be observed with Visual Studio 2017.

Answer 1

Under the Tools menu, choose Options. Then under Projects and Solutions, the Build and Run page has a field "maximum number of parallel project builds".

Answer 2

Make sure you don't have the /MP switch on any of your projects.

Then setting the maximum parallel project builds will directly relate to the number of compilation executable instances.

Will probably be slower. An alternative is to force Visual Studio/MSBuild to a specific affinity. This will not limit threads, but will keep some spare cores for the operating system/other programs.

Answer 3

I think you need to read this where the conclusion is that you need to set up your compilation to fit VS idea of the world.

Also limit the number of parallel projects to 2-3 depending on the actual PC you run it on. If your PC is a monster with 16+ cores you might be able to go 1-2 up.

Ideally VS should have offered an option of using X threads but alas.

Answer 4

To limit number of cl.exe you should use this option (at least it exists in MSVC 2015). Zero by default it means "number of CPUs" (if i'm not mistaken).