RFR(S): Parallelize CLDG and CodeCache root scanning and evacuation

[Zhengyu Gu]

Hi,

This investigation was based Roman's suggestion. By parallelizing CLDG and CodeCahe root scanning and evacuation, it results about
4% improvement of critical-jOPS without much impact on max-jOPS on SPECjbb2015 tests.


Webrev: http://cr.openjdk.java.net/~zgu/par-scan/webrev.01/


Thanks,

-Zhengyu