Bug ID: JDK-8303483 Enable NMT in summary mode by default

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It will be very useful to enable NMT by default. Currently, the following option needs to be added to the command line to enable NMT in summary mode:

-XX:NativeMemoryTracking=summary

If this option is not added to the command line at the process launch time, it is not possible to collect NMT output from the process without stopping and re-starting it again.

I moved this issue out of 22 into 23. It's blocked by JDK-8317453 Testing with JDK-8317453 reveals that current NMT memory overhead is too much (in Java2Demo) at about 7-9% overhead, to be able to turn it ON without some extra work. We can probably make it work by controlling malloc overhead and making NMT header smaller. It looks doable, but not in 22 timeframe.
09-11-2023
Maybe we could track only a subset of NMT allocation types ON by default, just enough to track RSS of general interest for example?
08-03-2023
Yeah, I agree with David. The overhead of NMT doesn't seem to be well-explained however, other than the "5-10%" overhead cited. I think that the work here is more experimental and social: Do experiments to show the overhead of NMT and explain them to the users so that they can make well-informed decisions.
08-03-2023
NMT has to be an opt-in facility because of the overheads.
02-03-2023

Blocks :	JDK-8317453 - NMT: Performance benchmarks are needed to measure speed and memory
Relates :	JDK-8303484 - Add the ability to enable NMT at runtime