RFR: JDK-8267348: Rewrite gc/epsilon/TestClasses.java to use Metaspace with less classes

[Thomas Stuefe]

On Wed, 19 May 2021 21:24:09 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> test/hotspot/jtreg/gc/epsilon/TestClasses.java line 34:
>> 
>>> 32:  *          java.base/jdk.internal.misc
>>> 33:  *
>>> 34:  * @run main/othervm -Xmx1g -XX:MetaspaceSize=1m -XX:MaxMetaspaceSize=64m -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xlog:gc -Xlog:gc+metaspace gc.epsilon.TestClasses
>> 
>> Why is the heap size increase necessary?
>
> Because this is Epsilon: the new allocations we in field blocks will never be collected. (This is also why the test precomputes the field names, trying not to do that for every class). Look at final "Heap:" messages before/after. Wanted to be on a safe side, so increased it above the 256m it seems to need on my machine. Most other Epsilon tests use `-Xmx1g` anyway.

Ah, right. Thanks for the clarification.

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PR: https://git.openjdk.java.net/jdk/pull/4118