[jdk21u-dev] RFR: 8293850: need a largest_committed metric for each category of NMT's output

[María Arias de Reyna]

This is a backport for https://bugs.openjdk.org/browse/JDK-8293850 (need a largest_committed metric for each category of NMT's output) needed in preparation to backport https://bugs.openjdk.org/browse/JDK-8320061 ( [nmt] Multiple issues with peak accounting )

This backport adds peak usage of the memory to the NMT output to be able to detect spikes.

Example of usage before the fix:


$ jcmd 160812 VM.native_memory detail | grep "mmap: reserved="
                            (mmap: reserved=8388608KB, committed=1277952KB) 
                            (mmap: reserved=528392KB, committed=55348KB) 
                            (mmap: reserved=197140KB, committed=58260KB) 
                            (mmap: reserved=40KB, committed=36KB) 
                            (mmap: reserved=8KB, committed=8KB) 
                            (mmap: reserved=262144KB, committed=244864KB) 
                            (mmap: reserved=1048576KB, committed=34816KB) 


After the fix (I just started the app, I wasn't really expecting any peak at this point):


$ jcmd 161688 VM.native_memory detail | grep "mmap: reserved="
                            (mmap: reserved=8388608KB, committed=507904KB, largest_committed=0KB) 
                            (mmap: reserved=1048576KB, committed=31232KB, largest_committed=0KB) 
                            (mmap: reserved=528392KB, committed=32836KB, largest_committed=0KB) 
                            (mmap: reserved=197140KB, committed=43220KB, largest_committed=0KB) 
                            (mmap: reserved=40KB, committed=36KB, largest_committed=0KB) 
                            (mmap: reserved=8KB, committed=8KB, largest_committed=0KB) 
                            (mmap: reserved=262144KB, committed=216640KB, largest_committed=0KB)

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

Commit messages:
 - Backport 8647f001bbb804503e8491d10f77aa0f34d66bf2

Changes: https://git.openjdk.org/jdk21u-dev/pull/440/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=440&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293850
  Stats: 42 lines in 4 files changed: 29 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/440.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/440/head:pull/440

PR: https://git.openjdk.org/jdk21u-dev/pull/440