[jdk21u-dev] RFR: 8320061: [nmt] Multiple issues with peak accounting [v3]

[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. The pull request contains three additional commits since the last revision:

 - Merge master
 - Backport dc256fbc6490f8163adb286dbb7380c10e5e1e06
 - Backport 8647f001bbb804503e8491d10f77aa0f34d66bf2

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

Changes:
  - all: https://git.openjdk.org/jdk21u-dev/pull/481/files
  - new: https://git.openjdk.org/jdk21u-dev/pull/481/files/462bec00..77ac5fee

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=481&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=481&range=01-02

  Stats: 6570 lines in 271 files changed: 4096 ins; 1409 del; 1065 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