> From: Christopher Schultz [mailto:ch...@christopherschultz.net] 
> Subject: Re: Performance issue 8.5.20 (metaspace related?)
> > > That sounds like a healthy behavior to me. That means GC is
> > > occurring and Metaspace is getting cleaned up. Why do you think
> > > Metaspace is the problem?

> > Because I can observe that when the metaspace is collected the
> > requests become fast. I observer that a few hours ago, looking at
> > the metaspace graph of the java console and doing requests just
> > after the collect.

> RMI is known for flagrantly wasting permgen/metaspace because of all
> the Proxy objects and special throw-away Class objects it uses, etc.
> But I'm not sure why the metaspace filling up would have such a
> dramatic effect on performance.

> At any rate, this is not a problem with Tomcat itself: this is likely
> entirely JVM-related.

Is it possible that the system is getting into swapping?  The heap has been
set to 20 GiB, but I didn't see any mention of how much actual memory the
system has.  Do you really need a 20 GiB heap?  Sometimes smaller is better.
Might also want to try turning off UseHugeTLBFS.

I wonder if there are heap objects tied up due to dead but not collected
metaspace items; when metaspace is GC'd, the heap usage might well shrink
also.  (This might be a G1GC bug, but that seems unlikely.)  Perhaps the RMI
mechanism (which I haven't looked at in many years) is searching an
ever-growing set of soft/weak references that are removed when metaspace is
collected.  A smaller heap might help there.

 - Chuck

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