Metaspace high watermark exceeds MaxMetaspaceSize

[Rui Li]

Hello,

I'm using JDK 11.0.13 and G1GC. Our application needs to dynamically
load lots of classes so I'm monitoring our metaspace usage. I noticed that
the high watermark can exceed the MaxMetaspaceSize and I wonder whether
this is expected behavior? Any suggestions would be appreciated!

Below is the output of jcmd VM.metaspace:

Total Usage ( 35182 loaders):

  89645 chunks,   383.36 MB capacity,   340.29 MB ( 89%) used,    37.58 MB
( 10%) free,    19.78 KB ( <1%) waste,     5.47 MB (  1%) overhead,
deallocated: 52608 blocks with 17.04 MB

Virtual space:
    628.00 MB reserved,     627.25 MB (>99%) committed



Chunk freelist:

 specialized chunks:    3, capacity 3.00 KB
       small chunks: 30762, capacity 120.16 MB
      medium chunks: 1976, capacity 123.50 MB
   humongous chunks: (none)
              Total: 32741, capacity=243.67 MB

Waste (percentages refer to total committed size 627.25 MB):
              Committed unused:    228.00 KB ( <1%)
        Waste in chunks in use:     19.78 KB ( <1%)
         Free in chunks in use:     37.58 MB (  6%)
     Overhead in chunks in use:      5.47 MB ( <1%)
                In free chunks:    243.67 MB ( 39%)
Deallocated from chunks in use:     17.04 MB (  3%) (52608 blocks)
                       -total-:    304.00 MB ( 48%)


MaxMetaspaceSize: 768.00 MB
InitialBootClassLoaderMetaspaceSize: 4.00 MB
UseCompressedClassPointers: false
No class space
Initial GC threshold: 512.00 MB
Current GC threshold: 836.34 MB
CDS: off

-- 
Best regards!
Rui Li
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