RFR: JDK-8293114: JVM should trim the native heap [v4]

[Thomas Stuefe]

On Thu, 6 Jul 2023 15:38:56 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

>> Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   last cleanups and shade feedback
>
> The description says `-XX:GCTrimNativeHeapInterval=<seconds> (defaults to 60)`, but the code says milliseconds.

Thanks @lkorinth @shipilev @robehn for the reviews.

Next version:
- renamed TrimNative namespace to NativeHeapTrimmer, the log tag to "trimnh", files, include guards etc
- Reworked the trimmer thread to:
   - uniformly use elapsedTime
   - Use atomics for the trim count
   - get rid of run_inner
   - made suspend count 16bit
   - tightened code around the trim loop
- added minimal gtest
- reworked jtreg test to use whitebox (which required a new WB method for pre-touching memory) and reshaped the test according to Alekseys suggestions.
- and lots of other smaller stuff.

Just went through the remarks again and I hope I got everything.

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PR Comment: https://git.openjdk.org/jdk/pull/14781#issuecomment-1625430752