Sometimes we want to turn down the number of workers on just one tree where the work is particularly memory-intense. Other trees shouldn't have to suffer for that.
The place to start is in config.py.
Commit pushed to master at https://github.com/mozilla/dxr https://github.com/mozilla/dxr/commit/dd918bee56dd39a1cb8d220466da226ea569dc49 Allow per-tree specification of worker count. Fixes bug 1288242. (#604) This way, we can keep RAM use low for hungry plugins but still aggressively parallelize other trees.