RFR: 8253332: ZGC: Make heap views reservation platform independent [v3]

[Per Lidén]

On Fri, 18 Sep 2020 09:25:43 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> ZVirtualMemoryManager::reserve_contiguous_platform tries to reserve three views of a given address range. The posix and
>> windows versions are more or less duplicates, with calls to platform dependent versions of reserve/unreserve functions.
>> I'd like to clean this up in preparation of an alternative implementation for heap memory allocation on Windows.
>> 
>> I choose to prefix the OS dependent functions with os_. For consistency, initialize_os should have been renamed as
>> well, but the plan is to change that in a separate patch that splits that function into two, so I skipped it for now.
>
> Stefan Karlsson has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review 2

src/hotspot/share/gc/z/zVirtualMemory.cpp line 136:

> 134:   if (reserve_contiguous_inner(start, size)) {
> 135:     // Make the address range free
> 136:     _manager.free(start, size);

I think we can just move these two lines to the end of reserve_contiguous_inner(), and remove this function.

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PR: https://git.openjdk.java.net/jdk/pull/236