> On Feb 15, 2024, at 09:04, Brian Braun <java08275...@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=3D340MB, commited=3D340MB) > (arena=3D340MB #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. > 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. - Chuck
