RFR: 8312132: Add tracking of multiple address spaces in NMT [v105]

[Johan Sjölen]

On Fri, 24 May 2024 07:06:54 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Lower number of pages
>
> src/hotspot/share/nmt/nmtNativeCallStackStorage.hpp line 95:
> 
>> 93:   Link** _buckets;
>> 94:   GrowableArrayCHeap<NativeCallStack, mtNMT> _stacks;
>> 95:   bool _is_detailed_mode;
> 
> _is_detailed: I somehow don't think this rather low level class should care about and copy the MemTracker state. I like "one truth only", which is MemTracker::enabled. I'd rather see this handled at the call site.
> 
> If we only need it to prevent allocation of the bucket table at construction time, I'd allocate that one with malloc.

It's not my favourite part either, but it should receive the truth from the `MemTracker::enabled`. 

>If we only need it to prevent allocation of the bucket table at construction time, I'd allocate that one with malloc.

It's also used for returning fake `StackIndex`:es for `VMATree` if we're in summary mode. I'll look more at this next week.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18289#discussion_r1614044361