RFR: 8261600: NMT: Relax memory order for updating MemoryCounter and fix racy updating of peak values

[Zhengyu Gu]

On Thu, 18 Feb 2021 03:44:27 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Currently, MemoryCounter is updated with default memory_order_conservative, it is too strong for updating a counter.
>> 
>> Also, updating peak values with regular assignment, which is racy and broken.
>> 
>> - [x] hotspot_nmt on Linux x86_64 and aarch64
>
> Hi Zhengyu,
> 
> This seems okay. 
> 
> Thanks,
> David

Thanks for reviewing, @dholmes-ora and @shipilev

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PR: https://git.openjdk.java.net/jdk/pull/2527