MHU: Downsweep can be quite slow with a lot of modules and packages (1800 modules/139 packages)
It seems there is some opportunity to improve the speed and progress reporting of downsweep.
- When you have a lot of packages an option to indicate progress would be nice (related to #20877)
- Seems that there is some opportunity for parallelism, can assign n packages per thread and have thread-local storage to store the downsweep cache. (To avoid global lock on the cache).
- Some normal profiling to make sure there's no obvious hotspots (ie looking things up in long lists).