RFR: 8305994: Guarantee eventual async monitor deflation [v7]

[Daniel D. Daugherty]

On Tue, 18 Apr 2023 16:36:34 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> See discussion in the bug. This PR introduces a safety rail that kicks in when the threshold heuristics fails, and it is cleanly backportable to JDK 17, where the problem manifests as apparent memory leak. There are other options to resolve this (see the bug), but I think this one is the easiest in the interim. 
>> 
>> Additional testing:
>>  - [x] Linux x86_64 `tier1`
>>  - [x] Linux x86_64 `tier2`
>>  - [x] Linux x86_64 `tier3`
>>  - [x] `runtime/Monitor` tests
>>  - [x] Ad-hoc experiments (see example in the bug)
>>  - [x] New feature test
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 12 additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8305994-async-deflate
>  - Build fixes and cleanups
>  - Merge branch 'master' into JDK-8305994-async-deflate
>  - More review comments and improvements
>  - Volker is right again (fixing unsigned underflow)
>  - Sort imports
>  - Volker is right
>  - Make the no-progress bit cleaner
>  - Copyright updates
>  - Touchup the option description
>  - ... and 2 more: https://git.openjdk.org/jdk/compare/69f891d2...17eb1036

Thumbs up. I like the new test!!

Your new GuaranteedAsyncDeflationInterval option gets us back
to having a deflation cycle triggered regardless of the thresholds.
Way back that was done as part of safepoint cleanup and now
that's done with your new option. I like the safety net.

test/hotspot/jtreg/runtime/Monitor/GuaranteedAsyncDeflationIntervalTest.java line 2:

> 1: /*
> 2:  * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.

Should there be a copyright year in Amazon's notice?

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Marked as reviewed by dcubed (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13474#pullrequestreview-1394856255
PR Review Comment: https://git.openjdk.org/jdk/pull/13474#discussion_r1173157431