RFR: OWST competitive spin master

[Roman Kennke]

This looks like a great enhancement!

One minor nit:

You've got this a few times:
+      MonitorLockerEx locker(_blocker, true);   // no safepoint check

I'd write it like this:
MonitorLockerEx locker(_blocker, Mutex::_no_safepoint_check_flag);

No need for another review for that little change.

Cheers,
Roman

Am Montag, den 07.11.2016, 11:11 -0500 schrieb 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.0
> 0/
> 
> Thanks,
> 
> -Zhengyu
> 
>