RFR: 8320370: NMT: Change MallocMemorySnapshot to simplify code. [v2]

[Zhengyu Gu]

On Mon, 20 Nov 2023 13:41:43 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> I believe the reason for the original shape of this code was to avoid initialization altogether if NMT was disabled. @zhengyu123 ?

The original code was to workaround 

> I believe the reason for the original shape of this code was to avoid initialization altogether if NMT was disabled. @zhengyu123 ?

I believe it was coded this way to avoid memory allocation (malloc) during NMT initialization, before tracking infrastructure is ready, e.g. `MallocSiteTable` is initialized.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/16724#issuecomment-1821006023