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

[Aleksey Shipilev]

On Thu, 11 Feb 2021 15:05:17 GMT, Zhengyu Gu <zgu 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

This looks fine to me too.

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Marked as reviewed by shade (Reviewer).

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