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List:       tomcat-user
Subject:    Re: Tomcat/Java starts using too much memory and not by the heap or non-heap memory
From:       Christopher Schultz <chris () christopherschultz ! net>
Date:       2024-02-16 15:26:06
Message-ID: cf372022-8c74-47d1-af31-5c15742430c7 () christopherschultz ! net
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Chuck and Brian,

On 2/15/24 10:53, Chuck Caldarale wrote:
> 
> > On Feb 15, 2024, at 09:04, Brian Braun <java08275660@gmail.com> wrote:
> > 
> > I discovered the JCMD command to perform the native memory tracking. When
> > running it, after 3-4 days since I started Tomcat, I found out that the
> > compiler was using hundreds of MB and that is exactly why the Tomcat
> > process starts abusing the memory! This is what I saw when executing "sudo jcmd \
> > <TomcatProcessID> VM.native_memory scale=MB": 
> > Compiler (reserved=340MB, commited=340MB)
> > (arena=340MB #10)
> > 
> > Then I discovered the Jemalloc tool (http://jemalloc.net <http://jemalloc.net/>) \
> > and its jeprof tool, so I started launching Tomcat using it. Then, after 3-4 days \
> > after Tomcat starts I was able to create some GIF images from the dumps that
> > Jemalloc creates. The GIF files show the problem: 75-90% of the memory is
> > being used by some weird activity in the compiler! It seems that something
> > called "The C2 compile/JIT compiler" starts doing something after 3-4 days,
> > and that creates the leak. Why after 3-4 days and not sooner? I don't know.
> 
> 
> There have been numerous bugs filed with OpenJDK for C2 memory leaks over the past \
> few years, mostly related to recompiling certain methods. The C2 compiler kicks in \
> when fully optimizing methods, and it may recompile methods after internal \
> instrumentation shows that additional performance can be obtained by doing so. 
> 
> > I am attaching the GIF in this email.
> 
> 
> Attachments are stripped on this mailing list.

> (

I'd love to see these.

> > Does anybody know how to deal with this?
> 
> 
> You could disable the C2 compiler temporarily, and just let C1 handle your code. \
> Performance will be somewhat degraded, but may well still be acceptable. Add the \
> following to the JVM options when you launch Tomcat: 
> -XX:TieredStopAtLevel=1
> 
> 
> > By the way, I'm running my website using Tomcat 9.0.58, Java
> > "11.0.21+9-post-Ubuntu-0ubuntu122.04", Ubuntu 22.04.03. And I am developing
> > using Eclipse and compiling my WAR file with a "Compiler compliance
> > level:11".
> 
> 
> You could try a more recent JVM version; JDK 11 was first released over 5 years \
> ago, although it is still being maintained.

There is an 11.0.22 -- just a patch-release away from what you appear to
have. I'm not sure if it's offered through your package-manager, but you
could give it a try directly from e.g. Eclipse Adoptium / Temurin.

Honestly, if your code runs on Java 11, it's very likely that it will
run just fine on Java 17 or Java 21. Debian has packages for Java 17 for
sure, so I suspect Ubuntu will have them available as well.

Debian-based distros will allow you to install and run multiple
JDKs/JREs in parallel, so you can install Java 17 (or 21) without
cutting-off access to Java 11 if you still want it.

-chris

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