RFR: JDK-8319314: NMT detail report slow or hangs for large number of mappings [v2]

[Thomas Stuefe]

On Wed, 8 Nov 2023 15:50:51 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

>> Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix builds
>
> src/hotspot/share/nmt/memBaseline.cpp line 119:
> 
>> 117:                          AllocFailStrategy::RETURN_NULL> EntryList;
>> 118:   EntryList _virtual_memory_regions;
>> 119:   size_t    _count;
> 
> Why are we bothering with `_count` ? I might be missing something, but I don't see it being used?

No idea. I guess this is a remnant, and could probably be removed, but ideally in another cleanup PR.

> src/hotspot/share/nmt/memBaseline.cpp line 126:
> 
>> 124: #ifdef ASSERT
>> 125:     , _last_base(nullptr)
>> 126: #endif
> 
> Why not use:
> 
> `DEBUG_ONLY(, _last_base(nullptr))`
> 
> just like in other places where `_last_base` is used?

I think that won't compile. I don't remember the exact reason, but DEBUG_ONLY does not work for initializer lists.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16480#discussion_r1387740579
PR Review Comment: https://git.openjdk.org/jdk/pull/16480#discussion_r1387738126