[jdk21u-dev] RFR: 8320061: [nmt] Multiple issues with peak accounting [v2]

[María Arias de Reyna]

> This is a follow up of https://github.com/openjdk/jdk21u-dev/pull/440
> 
> This backport fixes several NMT things, among those, the problem with largest_committed being 0KB as shown on the previous PR.
> 
> Example of output:
> 
> 
> $ jcmd 20088 VM.native_memory detail | grep "mmap: reserved="
>                             (mmap: reserved=8388608KB, committed=618496KB, at peak) 
>                             (mmap: reserved=1048576KB, committed=32064KB, at peak) 
>                             (mmap: reserved=528392KB, committed=41416KB, at peak) 
>                             (mmap: reserved=197140KB, committed=45380KB, at peak) 
>                             (mmap: reserved=40KB, committed=36KB, at peak) 
>                             (mmap: reserved=8KB, committed=8KB, at peak) 
>                             (mmap: reserved=262144KB, committed=224640KB, at peak) 
>                             (mmap: reserved=0KB, committed=0KB, peak=20KB) 
> 
> As described in the original PR, other features in this PR is fixing the scale so it also shows when the allocation value is zero (note the GB now instead of showing KB as before, and the *0GB* that is shown):
> 
> 
> $ jcmd 20088 VM.native_memory detail scale=g | grep "committed"
> Total: reserved=11GB, committed=2GB
>        mmap:   reserved=10GB, committed=1GB
> -                 Java Heap (reserved=8GB, committed=1GB)
>                             (mmap: reserved=8GB, committed=1GB, at peak) 
> -                     Class (reserved=1GB, committed=0GB)
>                             (mmap: reserved=1GB, committed=0GB, at peak) 
>                             (    reserved=0GB, committed=0GB)
>                             (    reserved=1GB, committed=0GB)
> -                      Code (reserved=1GB, committed=0GB)
>                             (mmap: reserved=1GB, committed=0GB, at peak) 
> -                     Other (reserved=1GB, committed=1GB)
> 	[0x00000005c0000000 - 0x0000000601c00000] committed 1GB from
>                              (reserved=8GB, committed=1GB Type=Java Heap)
>                              (reserved=1GB, committed=0GB Type=Class)
>                              (reserved=1GB, committed=0GB Type=Code)

María Arias de Reyna has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase.

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Changes:
  - all: https://git.openjdk.org/jdk21u-dev/pull/481/files
  - new: https://git.openjdk.org/jdk21u-dev/pull/481/files/462bec00..462bec00

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=481&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=481&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/481.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/481/head:pull/481

PR: https://git.openjdk.org/jdk21u-dev/pull/481