RFR: 8198668: MemoryPoolMBean/isUsageThresholdExceeded/isexceeded001/TestDescription.java still failing [v4]

[Kevin Walls]

> Test has been problemlisted for a long time due to intermittent failures.
> 
> This is a difficult test as it tries to monitor usage thresholds on Memory Pools which are outside its control.
> Not just Java heap pools, where the allocation it makes may or may not affect a particuclar pool, but non-heap pools such as CodeHeap and Metadata, where other activity in the VM can affect their usage and surprise the test.
> 
> The test iterates JMX memory pools where thresholds are supported, sets a threshold one byte higher than current usage, and makes an allocation.  This only makes sense on Java heap pools.  It is tempting to skip non-heap pools, but this test can still give a sanity test about threshold behaviour.  That is actually its main purpose, as the allocation is unlikely to affect the pool being tested.
> 
> With the changes here, I'm seeing the test and all its variations pass reliably, i.e. 50 iterations in each tested platform.
> 
> Skip testing a non-heap memory pool, e.g. CodeHeap, if it is hitting the threshold while we test, because that means it is changing outside our control.  Also re-test isExceeded on failure, as fetching the usage and isExceeded is a race.
> 
> Logging of more pool stats to better understand failures.

Kevin Walls has updated the pull request incrementally with one additional commit since the last revision:

  Comment update

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9309/files
  - new: https://git.openjdk.org/jdk/pull/9309/files/d2bf8b37..12e08d67

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9309&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9309&range=02-03

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9309.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9309/head:pull/9309

PR: https://git.openjdk.org/jdk/pull/9309