import javax.management.*;
import javax.management.openmbean.CompositeData;
import com.sun.management.GcInfo;
import com.sun.management.GarbageCollectionNotificationInfo;

sclass GCPause {
  long start, duration;
  S name, cause, action;
  
  toString {
    ret "GCPause duration=" + duration + " ms, start=" + start + " (VM time). " + renderStructs(+name, +cause, +action);
  }
}

static new Flag collectGCPauses_started;
static L<GCPause> collectGCPauses_list;

static void collectGCPauses() {
  collectGCPauses(1000);
}

static void collectGCPauses(int bufferSize) {
  if (!collectGCPauses_started.raise()) ret;
  collectGCPauses_list = synchroList(LatestList(bufferSize));
  
  onGCNotification(voidfunc(GarbageCollectionNotificationInfo info) {
    GcInfo gcInfo = info.getGcInfo();
    GCPause pause = nu(GCPause,
      start := gcInfo.getStartTime(),
      duration := gcInfo.getDuration(),
      name := info.getGcName(),
      cause := info.getGcCause(),
      action := info.getGcAction());
    collectGCPauses_list.add(pause);
  });
}

Began life as a copy of #1013400