RFR: 8262398: Shenandoah: Disable nmethod barrier and stack watermark when running with passive mode [v4]

[Roman Kennke]

On Tue, 16 Mar 2021 17:52:26 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> nmethod barrier and stack watermark allow GC not to process nmethods at GC pauses, and aim to reduce GC latency, they do not benefit STW GCs, who process nmethods at pauses anyway.
>> 
>> Test:
>> 
>> - [x] hotspot_gc_shenandoah
>> - [x] tier1 with -XX:+UseShenandoahGC
>> - [x] tier1 with -XX:+UseShenandoahGC -XX:ShenandoahGCMode=passive
>> - [x]  tier1 with -XX:+UseShenandoahGC -XX:ShenandoahGCMode=passive -XX:-ShenandoahDegeneratedGC
>
> Zhengyu Gu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix spaces

Looks good! Thanks!

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2727