JDK 13 EA: 100% CPU use with no Java threads runnable

Erik Gahlin erik.gahlin at oracle.com
Sun Sep 15 09:57:59 UTC 2019

There is also JFR.

$ java -XX:StartFlightRecording:filename=dump.jfr …


$ jcmd <pid> JFR.start duration=10s filename=dump.jfr

Open the file in JMC and select Native Method Sample. It will show threads that are in native. You can also print the events from command line, but it may a bit too many samples, i.e.

$ jfr print —events NativeMethodSample,CPULoad dump.jfr


> On 14 Sep 2019, at 22:57, Stefan Reich <stefan.reich.maker.of.eye at googlemail.com> wrote:
> Hi,
> I was advised by Oracle's Fairoz Matte to contact this list.
> I am seeing a Java process use 100% of one CPU core continuously, but no
> Java threads are runnable (as evidenced by internal thread sampling as well
> as VisualVM).
> Whenever it occurs, the problem does not seem to go away until the Java VM
> exits.
> I think I am using a single native library (OSHI), the rest is pure Java.
> Older versions of the JDK have exhibited the same problem, but most
> interestingly, the bug is happening right now on a Linux machine
> (Peppermint 7 I think) with OpenJDK 13 EA Build 31.
> I can perform any test on this machine that you instruct me to.
> Please advise,
> Stefan
> -- 
> Stefan Reich
> BotCompany.de // Java-based operating systems

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