test/hotspot/jtreg/serviceability/jvmti/HeapMonitor/MyPackage/HeapMonitorThreadTest.java

rev 49267 : [mq]: event5
rev 49268 : [mq]: event6
rev 49269 : [mq]: event7

@@ -41,11 +41,10 @@
     final int numThreads = 24;
     ArrayList<Thread> list = new ArrayList<>();
 
     // Remember a lot of garbage to have space for all thread samples.
     HeapMonitor.enableSamplingEvents();
-    HeapMonitor.setGarbageHistory(10000);
 
     for (int i = 0 ; i < numThreads; i++) {
       Thread thread = new Thread(new Allocator(i), "Allocator" + i);
       thread.start();
       list.add(thread);

@@ -65,38 +64,41 @@
   }
 }
 
 class Allocator implements Runnable {
   private int depth;
-  private volatile int tmp[];
+  private List<int[]> currentList;
 
   public Allocator(int depth) {
     this.depth = depth;
   }
 
-  private int helper() {
-    int sum = 0;
-    // Let us assume that the array is 24 bytes of memory.
-    for (int i = 0; i < 127000 / 6; i++) {
+  private void helper() {
+    List<int[]> newList = new ArrayList<>();
+    // Let us assume that the array is 24 bytes of memory, by default we sample at 512k, keep in
+    // memory at least 2MB without counting the link-list itself, which adds to this.
+    int iterations = (1 << 21) / 24;
+    for (int i = 0; i < iterations; i++) {
       int newTmp[] = new int[1];
       // Force it to be kept.
-      tmp = newTmp;
-      sum += tmp[0];
+      newList.add(newTmp);
     }
-    return sum;
+
+    // Replace old list with new list, which provokes two things:
+    //  Old list will get GC'd at some point.
+    //  New list forces that this thread has some allocations still sampled.
+    currentList = newList;
   }
 
-  private int recursiveWrapper(int depth) {
+  private void recursiveWrapper(int depth) {
     if (depth > 0) {
-      return recursiveWrapper(depth - 1);
+      recursiveWrapper(depth - 1);
     }
-    return helper();
+    helper();
   }
 
   public void run() {
-    int sum = 0;
     for (int j = 0; j < 50; j++) {
-      sum += recursiveWrapper(depth);
+      recursiveWrapper(depth);
     }
-    System.out.println(sum);
   }
 }