[jdk21u-dev] RFR: 8337994: [REDO] Native memory leak when not recording any events

[Boris Ulasevich]

On Thu, 24 Oct 2024 13:54:06 GMT, Boris Ulasevich <bulasevich at openjdk.org> wrote:

> (not a clean backport)
> Reworked to avoid https://github.com/openjdk/jdk/pull/17328/files  backport

Reproducer:

import jdk.jfr.consumer.RecordingStream;

/**
  * Stress test to provoke the memory leak:
  * starts 1M empty threads in VM with jfr recording
  */
public class PinnedThreadTracker implements AutoCloseable
{
    private final RecordingStream recordingStream;

    public PinnedThreadTracker() {
        recordingStream = new RecordingStream();
        recordingStream.startAsync();
        System.out.println("start recording..");
    }

    @Override
    public void close() {
        recordingStream.close();
    }

    class MyThread extends Thread {
        public void run() {
        }
    }
    public void runThreads() {
        for (int i = 0; i < 100; i++) {
            for (int j = 0; j < 100; j++) {
                for (int k = 0; k < 100; k++) {
                    new MyThread().start();
                }
                MyThread thr = new MyThread(); thr.start();
                try {
                    thr.join();
                } catch (Exception ex) {}
            }
            System.out.print(".");
        }
    }

    public static void main(String a[]) {
        PinnedThreadTracker ptt = new PinnedThreadTracker();
        ptt.runThreads();
        ptt.close();
    }
}	


Manual testing results on jdk21u:

$ for i in {0..60}; do
    export PID=`ps -ax | grep java | grep PinnedThreadTracker | sed "s/^ *// ; s/ .*//"`
    jcmd $PID VM.native_memory | grep Tracing.*reserved
    sleep 1s
  done

Before the change (jcmd VM.native_memory output once a second):
-                   Tracing (reserved=17355KB, committed=17355KB)
-                   Tracing (reserved=21646KB, committed=21646KB)
-                   Tracing (reserved=25870KB, committed=25870KB)
-                   Tracing (reserved=30065KB, committed=30065KB)
...
-                   Tracing (reserved=240567KB, committed=240567KB)
-                   Tracing (reserved=244519KB, committed=244519KB)
-                   Tracing (reserved=248525KB, committed=248525KB)
-                   Tracing (reserved=252527KB, committed=252527KB)

With the fix:
-                   Tracing (reserved=17655KB, committed=17655KB)
-                   Tracing (reserved=18125KB, committed=18125KB)
-                   Tracing (reserved=18449KB, committed=18449KB)
-                   Tracing (reserved=18961KB, committed=18961KB)
...
-                   Tracing (reserved=17443KB, committed=17443KB)
-                   Tracing (reserved=17958KB, committed=17958KB)
-                   Tracing (reserved=18491KB, committed=18491KB)
-                   Tracing (reserved=18970KB, committed=18970KB)

-------------

PR Comment: https://git.openjdk.org/jdk21u-dev/pull/1095#issuecomment-2455300319