RFR: 8257901: ZGC: Take virtual memory usage into account when sizing heap [v2]

[Per Liden]

On Wed, 9 Dec 2020 11:26:17 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Per Liden has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Review StefanK
>
> src/hotspot/share/gc/shared/gcArguments.cpp line 178:
> 
>> 176: size_t GCArguments::heap_virtual_to_physical_ratio() {
>> 177:   // Used by heap size heuristics to determine max amount
>> 178:   // of address space to use for the heap.
> 
> Could this explanation moved to the hpp file? Then some IDEs will automatically pick it up. I'd expect a comments to the implementation, i.e. of the value 1 here instead of a generic explanation of what the method does.

Ok, I'll move the comment.

> src/hotspot/share/runtime/arguments.cpp line 1658:
> 
>> 1656: }
>> 1657: 
>> 1658: julong Arguments::limit_heap_by_allocatable_memory(julong limit) {
> 
> If we are already messing with the name in this change, would it be possible to change return value and parameter to `size_t`? I'm good with moving this change of the parameter types to a different issue, but as mentioned, since we are already changing stuff around here...

I'd prefer to handle that as a separate issue, since such a change would propagate into `os::has_allocatable_memory_limit()` and affect all os:es.

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PR: https://git.openjdk.java.net/jdk/pull/1696