Change maxdegreeofparallelism during execution?

[FrenziedIM]

I'm guessing this isn't possible, but by the slight chance it is, please let me know how to do it! I need to change the number of threads whilst the parallel loop is running.

My other option is using cancellation tokens, but they seem to be very slow. Is there not a fast way to just completely exit the parallelforeachasync? Might have to result to a application restart, but was wondering if someone could help me this.