RFR: 8255973: Add more logging to debug JDK-8255917

[Calvin Cheung]

On Tue, 10 Nov 2020 23:23:29 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.

Looks good. Some nits below.

src/hotspot/share/services/virtualMemoryTracker.cpp line 387:

> 385:       if (reserved_rgn->flag() == mtClassShared) {
> 386:         log_info(nmt)("CDS reserved region \'%s\' as a whole type class (" INTPTR_FORMAT ", " SIZE_FORMAT ")",
> 387:                       reserved_rgn->flag_name(), p2i(reserved_rgn->base()), reserved_rgn->size());

Since you're logging the region name, I don't think you need to say `type class`.

src/hotspot/share/services/virtualMemoryTracker.cpp line 396:

> 394:       if (reserved_rgn->flag() == mtJavaHeap) {
> 395:         log_info(nmt)("CDS reserved region \'%s\' as a whole type heap " INTPTR_FORMAT ": " SIZE_FORMAT,
> 396:                       reserved_rgn->flag_name(), p2i(reserved_rgn->base()), reserved_rgn->size());

Since you're logging the region name, I don't think you need to say `type heap`.

src/hotspot/share/services/virtualMemoryTracker.hpp line 309:

> 307:   void  set_flag(MEMFLAGS flag);
> 308:   inline MEMFLAGS flag() const            { return _flag;  }
> 309:   // uncommitted thread stack bottom, above guard pages if there is any.

Line deleted by accident?

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Marked as reviewed by ccheung (Reviewer).

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