Limit thread usage in tests #5516
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widlarizer
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Nov 27, 2025
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I'm on board with the idea, but the variable seems to be applied in the wrong spot. Our testing automation is definitely suboptimal and we're making it a focus to figure out how to make it less painful, but right now, the variable seems to have to be applied in a couple of places, or in the top-level Makefile
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…overload systems when running 'make -j... test'
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widlarizer
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This is following up on discussion where we agreed to pursue making RTLIL safe for multithreaded read-only access.
What are the reasons/motivation for this change?
Yosys tests already run tests in parallel, potentially up to the point where the number of running tests equals the number of CPUs if the user uses
make -j test. If each test spawns a number of threads equal to the number of CPUs, the total number of threads could be quadratic in the number of CPUs, which could be bad.Instead limit each test to 4 threads.
This change also makes it easy to do scalability performance tests without using thread affinity tricks like
taskset.