RFR: 8287135: Calculation of jmm_GetMemoryUsage is wrong [v3]

[Ioi Lam]

On Tue, 7 Jun 2022 10:07:08 GMT, Yi Yang <yyang at openjdk.org> wrote:

>> It seems that calculation of MemoryMXBean.getNonHeapMemoryUsage(jmm_GetMemoryUsage) is wrong.
>> 
>> Currently, `NonHeapUsage=CodeCache+Metaspace(ClassTypeSpace+NonClassTypeSpace)+CompressedClassSpace(ClassTypeSpace)`
>> 
>> ==> CodeHeap 'non-nmethods' 1532544 (Used)
>> ==> CodeHeap 'profiled nmethods' 0
>> ==> CodeHeap 'non-profiled nmethods' 13952
>> ==> Metaspace 506696
>> ==> Compressed Class Space 43312
>> init = 7667712(7488K) used = 2096504(2047K) committed = 8454144(8256K) max = -1(-1K)
>> 
>> In this way, getNonHeapMemoryUsage is larger than it ought to be, it should be `NonHeapUsage = CodeCache + Metaspace`.
>
> Yi Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   update

@tstuefe could you take a look at the test changes. Since we can no longer query the compressed class space individually, I think the tests may become more lenient than before. For example, memoryUsageSmallComp/TestDescription.java uses `MemoryUsageTest::checkForNotGrowing()` which monitors the used bytes in `MetaspaceBaseGC::pool.getUsage().getUsed()`

- Before this PR, it checks that the usage of the compressed klass space doesn't grow.
- After this PR, it will allow the compresed klass space to grow, as long as the "other" meta space shrinks by a similar amount.

Is this OK? Or should we add a new whitebox API to query the compressed vs meta space?

src/hotspot/share/services/management.cpp line 743:

> 741:   } else {
> 742:     // Calculate the memory usage by summing up the pools.
> 743:     // NonHeapUsage = CodeHeaps + Metaspace

I think the new comments in this file can be removed.

test/hotspot/jtreg/vmTestbase/metaspace/gc/MemoryUsageTest.java line 141:

> 139:         System.err.println("Usage: ");
> 140:         System.err.println("java [-Xms..] [-XX:MetaspaceSize=..]  [-XX:MaxMetaspaceSize=..] \\");
> 141:         System.err.println("    " + MemoryUsageTest.class.getCanonicalName());

This method can be deleted since it's no longer used.

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PR: https://git.openjdk.java.net/jdk/pull/8831