RFR: JDK-8275608: runtime/Metaspace/elastic/TestMetaspaceAllocationMT2 too slow [v3]

[Thomas Stuefe]

> Small tweaks to make these elastic metaspace stress tests faster.
> 
> Before, runtime for individual tests was wobbling between 40+ seconds and some rare timeouts at 3+ minutes, depending on machine load and random luck. Now, we get a steadfast 35-37 seconds.
> 
> I tested this manually, checking the numbers that we really test what we want to test (a lot of arena activity). Also GHAs and SAP nightlies.
> 
> Thanks, Thomas

Thomas Stuefe has updated the pull request incrementally with two additional commits since the last revision:

 - Update test/hotspot/jtreg/runtime/Metaspace/elastic/RandomAllocator.java
   
   Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
 - Update test/hotspot/jtreg/runtime/Metaspace/elastic/RandomAllocator.java
   
   Co-authored-by: Aleksey Shipilëv <shade at redhat.com>

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6041/files
  - new: https://git.openjdk.java.net/jdk/pull/6041/files/8b5ebfd8..7101f3df

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6041&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6041&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6041.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6041/head:pull/6041

PR: https://git.openjdk.java.net/jdk/pull/6041