[Bug]: Rspack's Rust worker scheduling is uneven

[zhouxinyong]

System Info

System:
OS: macOS 14.6.1
CPU: (8) x64 Intel(R) Core(TM) i5-1038NG7 CPU @ 2.00GHz
Memory: 2.97 GB / 16.00 GB
Shell: 5.9 - /bin/zsh
Binaries:
Node: 20.18.1 - ~/.nvm/versions/node/v20.18.1/bin/node
Yarn: 1.22.22 - ~/.nvm/versions/node/v20.18.1/bin/yarn
npm: 10.8.2 - ~/.nvm/versions/node/v20.18.1/bin/npm
Browsers:
Chrome: 133.0.6943.99
Firefox: 124.0.2
Safari: 18.3

rspack v1.25

Details

From the above chart, it can be seen that Rspack's Rust worker scheduling is uneven, and the 19 workers are not being fully utilized. Can the thread pool be optimized to improve performance?

Reproduce link

No response

Reproduce Steps

This is an internal project of our company, so I apologize but I cannot provide the repository.

[JSerFeng]

The worker 19 seems to start at seal phase, so you can't see it work at make phase.

If you want to see the scheduling of various processes, it is best to use tools such as samply or instruments, and preferably without a js loader. If there is a js loader, the corresponding rust thread will wait for the js execution, while the js execution will be on the main thread.