RFR: JDK-8281460: Let ObjectMonitor have its own NMT category

[Aleksey Shipilev]

On Tue, 8 Feb 2022 08:10:05 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> It would be useful to distinguish ObjectMonitor allocations in NMT, as a simple way to both to see the needed footprint as well as the number of allocated monitors.
> 
> Note, this needs [JDK-8281450](https://bugs.openjdk.java.net/browse/JDK-8281450) as a prerequisite.

All right, but I also keep thinking that NMT becomes a wide-spread diagnostic interface, and at some point in the future we should probably exercise a bit of restraint in introducing overly-fine-grained categories.

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Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/7378