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

[Johan Sjölen]

On Thu, 23 May 2024 06:26:51 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
>
> test/hotspot/gtest/nmt/test_vmatree.cpp line 351:
> 
>> 349: struct SimpleVMATracker : public CHeapObj<mtTest> {
>> 350:   const size_t page_size = 4096;
>> 351:   enum Tpe { Reserved, Committed, Free };
> 
> Wow, we save one letter! ;-)

Think about it, that's one whole byte per instance in the code! Very useful when pushing changes over a 75 baud connection to Mars :-P! Fixed.

> test/hotspot/gtest/nmt/test_vmatree.cpp line 447:
> 
>> 445:     const size_t size = num_pages * page_size;
>> 446: 
>> 447:     const MEMFLAGS flag = (MEMFLAGS)(os::random() % mt_number_of_types);
> 
> I would maybe scale down, not use mt_number_of_types. 
> 
> We want to stress merging, too. So the total number of possible states should not that large. E.g. 8 states, with e.g. 4 flags and 2 stacks.

SGTM

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PR Review Comment: https://git.openjdk.org/jdk/pull/18289#discussion_r1611869340
PR Review Comment: https://git.openjdk.org/jdk/pull/18289#discussion_r1611868042