RFR: JDK-8318636: Add jcmd to print annotated process memory map [v4]

[Thomas Stuefe]

On Fri, 27 Oct 2023 15:42:06 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

>> Thomas Stuefe has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - Fix spelling
>>  - timeout fuse
>>  - Feedback Johan
>
> Taking a look...

@gerard-ziemski @jdksjolen I take this back to draft for the moment since I found that I need to solve at least two additional problems. 

One is the time it takes to correlate NMT regions with VMA - its O^2, and experiments with millions of mappings show that this does not scale well. My new plan is to pre-collect all NMT information available first in a flat cache-friendly array that can be iterated cheaply, possibly pre-sorted, and use that when iterating VMAs. And only do the first part in a VM Op.

The second problem is that the output can get huge and I run against limits in dcmd framework. I may just do what other commands do, dump to a file instead to the output.

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PR Comment: https://git.openjdk.org/jdk/pull/16301#issuecomment-1783735707