RFR: JDK-8293114: JVM should trim the native heap [v8]

[Thomas Stuefe]

On Wed, 12 Jul 2023 08:47:47 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Thomas Stuefe 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 32 additional commits since the last revision:
>> 
>>  - Make test spikes more pronounced
>>  - Dont query procfs if logging is off
>>  - rename logtag again
>>  - When probing for safepoint end, use the smaller of (interval, 250ms)
>>  - Remove TrimNativeHeap and expand TrimNativeHeapInterval
>>  - Improve comments for non-supportive platforms
>>  - Aleksey cosmetics
>>  - suspend count return 16 bits
>>  - Fix linker errors
>>  - Merge branch 'master' into JDK-8293114-JVM-should-trim-the-native-heap
>>  - ... and 22 more: https://git.openjdk.org/jdk/compare/9fd07c73...15566761
>
> One more thing, as I play with it: the GC logging does not have a comma before timestamp, see:
> 
> 
> [1.210s][info][trimnative] Trim native heap (1): RSS+Swap: 1192M->1191M (-1552K), 0.353ms
> [1.528s][info][gc        ] GC(0) Pause Young (Normal) (G1 Evacuation Pause) 91M->78M(1024M) 73.040ms
> 
> 
> Also, maybe the logging tag already says this is trimmer, and what we want to point out is this was periodic trim. The value in parentheses in GC logs is heap capacity, which makes trimmer delta confusing, but we can live with that. Do we really want to say "RSS+Swap" here? I think this would be cleaner:
> 
> 
> [3.214s][info][trimnative] Periodic Trim (1): 1261M->1197M (-65848K) 0.353ms

Thanks @shipilev!

We are closing in. 

Applied your patch, fixed Windows.

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PR Comment: https://git.openjdk.org/jdk/pull/14781#issuecomment-1634672151