RFR: 8255973: Add more logging to debug JDK-8255917 [v3]

[David Holmes]

On Thu, 12 Nov 2020 05:15:09 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:
> 
>   Make nmt log at debug level, and attempt_reserve_memory_at failed log to os+metaspace debug level

Changes requested by dholmes (Reviewer).

src/hotspot/share/runtime/os.cpp line 1672:

> 1670:     MemTracker::record_virtual_memory_reserve((address)result, bytes, CALLER_PC);
> 1671:   } else {
> 1672:     LogTarget(Debug, os, metaspace) lt;

You only needed to change:
`log_info(metaspace)("...");`
to
`log_debug(os, metaspace)("...")`

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