SourceKitService only using 50% of CPU

[flowtoolz (Sebastian Fichtner)]

@blangmuir

AST building for most requests is funneled through a serial queue. The only exceptions are the code-completion request, which has its own independent serial queue, and the "index" request, which should run fully in parallel. The serial behaviour is based on the kind of usage sourcekitd gets from clients like editors, where usually there is no reason to want to have two ASTs built in parallel (usually it's better to cancel any existing AST build when a new request comes in for a new edit or for a new document).

I was just trying to speed up codebase loading by parallelizing the LSP requests. Maybe someone can confirm or clarify my understanding:

When requesting symbols for different files in parallel, it seems, the requests are being processed serially (not faster) but correctly, so the requests are being buffered internally.

When requesting references for different symbols of the same file in parallel, it seems many requests are being cancelled when new requests come in, so they are not buffered internally.