RFR: 8255973: Add more logging to debug JDK-8255917 [v2]

[David Holmes]

On Wed, 11 Nov 2020 02:28:09 GMT, Yumin Qi <minqi at openjdk.org> wrote:

>> Hi, Please review
>> 
>>   JDK-8255917 failed on not finding the committed region from the _reserved_regions list when try to add the region to the committed list. It looks like possible the region was released without logged. 
>>   Added a log tag for tracing Native Memory Tracking (NMT) add/remove recorded info. This could help us to identify the problem for NMT or the code behind NMT. Function pd_attempt_reserve_memory_at could fail, but no message logged, so added a logging for its failure. 
>> 
>> Tests: tier1-4, local jtreg.
>
> Yumin Qi has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix the region extra type name

Hi Yumin,

I also have concerns about the safety of using UL in these low-level NMT routines as it is not obvious that you can't get into some kind of recursion situation.

More comments below.

Thanks,
David

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Changes requested by dholmes (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1150