RFR: 8271834: TestStringDeduplicationAgeThreshold intermittent failures on Shenandoah [v2]

[Per Liden]

On Fri, 10 Sep 2021 12:44:39 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> To trigger young GC, the test fills heap with -Xmn amount of garbage. However, -Xmn does not apply to non-generational GC, such as Shenandoah, and -Xmn amount of garbage, sometimes, it not enough to trigger GC, therefore, there is no guarantee that strings can reach deduplication age threshold.
>> 
>> I purpose to use MXBean to get exact gc count to ensure expected gc cycles actually performed.
>
> Zhengyu Gu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Aleksey's comment

test/hotspot/jtreg/gc/stringdedup/TestStringDeduplicationTools.java line 106:

> 104:                     if ("end of GC cycle".equals(info.getGcAction())) {
> 105:                         gcCount++;
> 106:                     }

I think you want to do the same thing for ZGC here, which also reports both pauses and cycles.

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PR: https://git.openjdk.java.net/jdk/pull/5428