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

[Robbin Ehn]

On Thu, 6 Jul 2023 16:14:20 GMT, Aleksey Shipilev <shade 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
>
> src/hotspot/share/runtime/trimNative.cpp line 149:
> 
>> 147:         return true;
>> 148:       } else {
>> 149:         log_info(trim)("Trim native heap (no details)");
> 
> Consistency: `Trim native heap: complete, no details`.

I would still like to know the trim_time.

> test/hotspot/jtreg/runtime/os/TestTrimNative.java line 247:
> 
>> 245:             System.out.println("Will spike now...");
>> 246:             for (int i = 0; i < numAllocations; i++) {
>> 247:                 ptrs[i] = Unsafe.getUnsafe().allocateMemory(szAllocations);
> 
> Pull `Unsafe.getUnsafe()` into a local or a field?

Maybe use WB instead of unsafe?

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PR Review Comment: https://git.openjdk.org/jdk/pull/14781#discussion_r1254816943
PR Review Comment: https://git.openjdk.org/jdk/pull/14781#discussion_r1254806836