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

[David Holmes]

On Wed, 11 Nov 2020 20:03:32 GMT, Yumin Qi <minqi at openjdk.org> wrote:

>> src/hotspot/share/runtime/os.cpp line 1672:
>> 
>>> 1670:     MemTracker::record_virtual_memory_reserve((address)result, bytes, CALLER_PC);
>>> 1671:   } else {
>>> 1672:     log_info(metaspace)("Attempt to reserve memory at " INTPTR_FORMAT " for "
>> 
>> Why is this logged for "metaspace"? I would use "os"
>
> Since we in this bug only concern about metaspace, if we specify -Xlog:os, it will output messaged we are not interested in from other places. I will wait for other inputs for this.

This is 'os' code so the logging should be in the os tag space, though it could be os+metaspace. I also think info is inappropriate and this should be debug or trace level. Alternatively put the logging in a caller that is more obviously only for metaspace.

>> src/hotspot/share/services/virtualMemoryTracker.cpp line 293:
>> 
>>> 291: void ReservedMemoryRegion::set_flag(MEMFLAGS f) {
>>> 292:   assert((flag() == mtNone || flag() == f),
>>> 293:          "Overwrite memory type for region [" INTPTR_FORMAT "-" INTPTR_FORMAT "), %u->%u.",
>> 
>> Why the explicit change to INTPTR_FORMAT? (real question, I actually do not know the difference to PTR_FORMAT, since their definition seems to be identical)
>
> They are defined as same, and p2i:
> inline intptr_t p2i(const void * p) {
>   return (intptr_t) p;
> }
> This way I think better use INTPTR_FORMAT, it is consistent with the type here.

I agree - semantically we use INTPTR_FORMAT when passing a p2i(x). Though it does beg the question as to why we are applying p2i in this case?

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