RFR: OWST competitive spin master

[Zhengyu Gu]

Hi,

I ran SPECjbb benchmark and some other GC intensive tests over past several days, I saw that OWST consistently outperforms current OpenJDK implementation.

Following are SPECjbb numbers from the same shenandoah jdk9 build:

OWST off: max-jOPS = 18092, critical-jOPS = 8461
OWST on:  max-jOPS = 18291, critical-jOPS = 8662

This changeset, competitive spin master enhancement, which lets spin master to give up its role when it is ready to go
into wait/sleep state, and lets other worker to take over to the role. The change seems further improved cirtical-jOPS.

OWST on: max-jOPS = 18291, critical-jOPS = 8850


Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/comp-owst/webrev.00/

Thanks,

-Zhengyu