RFR: 8157023: Integrate NMT with JFR

[Stefan Johansson]

On Thu, 1 Dec 2022 13:00:11 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Please review this enhancement to include NMT information in JFR recordings.
>> 
>> **Summary**
>> Native Memory Tracking summary information can be obtained from a running VM using `jcmd` if started with `-XX:NativeMemoryTracking=summary/detail`. Using `jcmd` requires you to run a separate process and to parse the output to get the needed information. This change adds JFR events for NMT information to enable additional ways to consume the NMT data.
>> 
>> There are two new events added:
>> * _NativeMemoryUsage_ - The total native memory usage.
>> * _NativeMemoryUsagePart_ - The native memory usage for each component.
>> 
>> These events are sent periodically and by default the interval is 1s. This can of course be discussed, but that is the staring point. When NMT is not enabled on events will be sent.
>> 
>> **Testing**
>> * Added a simple test to verify that the events are sent as expected depending on if NMT is enabled or not.
>> * Mach5 sanity testing
>
> src/hotspot/share/services/memReporter.cpp line 36:
> 
>> 34: #include "utilities/globalDefinitions.hpp"
>> 35: 
>> 36: size_t MemReporterBase::reserved_total(const MallocMemory* malloc, const VirtualMemory* vm) {
> 
> Why the const removal?

I turned `reserved_total(...)` and `committed_total(...)`into a static helpers since they did not use any members. That way my new reporter did not have to inherit `MemReporter`.

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PR: https://git.openjdk.org/jdk/pull/11449