6865703: G1: Parallelize hot card cache cleanup
Summary: Have the GC worker threads clear the hot card cache in parallel by having each worker thread claim a chunk of the card cache and process the cards in that chunk. The size of the chunks that each thread will claim is determined at VM initialization from the size of the card cache and the number of worker threads.
Reviewed-by: jmasa, tonyp
6843292: "Expect to be beyond new region unless impacting another region" assertion too strong
Summary: In the assertion allow for collision with the guard page.
Reviewed-by: tonyp, ysr, jcoomes