Svchost.exe is a bonkers bit of design that goes against the simple, basic separation of concerns that OS-level processes provide by running multiple "services" as DLLs loaded into one process. This makes it extremely hard to pinpoint which service is faulty.
That helps a little, but fundamentally the runtime of a module is still "billed" to the svchost.exe process as a whole - so if a particular one is at 100% of a cpu, you can't tell which module is causing the problem.
Apparently the magic runes are