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

[Aleksey Shipilev]

On Wed, 3 Apr 2024 11:16:23 GMT, María Arias de Reyna <duke at openjdk.org> wrote:

> 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)

This is ready for integration, is it not? Have some other backports, the cleanliness of which depends on this and JDK-8320061.

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PR Comment: https://git.openjdk.org/jdk21u-dev/pull/440#issuecomment-2071980328