test/jdk/java/lang/management/MemoryMXBean/ResetPeakMemoryUsage.java

@@ -46,10 +46,11 @@
 import java.lang.management.*;
 import java.lang.ref.WeakReference;
 import java.util.*;
 
 import sun.hotspot.code.Compiler;
+import sun.hotspot.WhiteBox;
 
 public class ResetPeakMemoryUsage {
     private static MemoryMXBean mbean = ManagementFactory.getMemoryMXBean();
     // make public so that it can't be optimized away easily
     public static Object[] obj;

@@ -65,11 +66,14 @@
         final String mn = "-Xmn8m";
         if (!Compiler.isGraalEnabled()) { // Graal does not support CMS
             RunUtil.runTestClearGcOpts(main, ms, mn, "-XX:+UseConcMarkSweepGC");
         }
         RunUtil.runTestClearGcOpts(main, ms, mn, "-XX:+UseParallelGC");
-        RunUtil.runTestClearGcOpts(main, ms, mn, "-XX:+UseG1GC", "-XX:G1HeapRegionSize=1m");
+        RunUtil.runTestClearGcOpts(main, ms, mn, "-XX:+UseG1GC", "-XX:-G1UseLegacyMonitoring",
+                                   "-XX:G1HeapRegionSize=1m");
+        RunUtil.runTestClearGcOpts(main, ms, mn, "-XX:+UseG1GC", "-XX:+G1UseLegacyMonitoring",
+                                   "-XX:G1HeapRegionSize=1m");
         RunUtil.runTestClearGcOpts(main, ms, mn, "-XX:+UseSerialGC",
                 "-XX:MarkSweepAlwaysCompactCount=1");
     }
 
     private static class TestMain {

@@ -77,20 +81,35 @@
             List pools = ManagementFactory.getMemoryPoolMXBeans();
             ListIterator iter = pools.listIterator();
             boolean found = false;
             while (iter.hasNext()) {
                 MemoryPoolMXBean p = (MemoryPoolMXBean) iter.next();
-                // only check heap pools that support usage threshold
-                // this is typically only the old generation space
-                // since the other spaces are expected to get filled up
+                // Only check heap pools that support a usage threshold.
+                // This is typically only the old generation space
+                // since the other spaces are expected to get filled up.
                 if (p.getType() == MemoryType.HEAP &&
-                    p.isUsageThresholdSupported())
-                {
+                    p.isUsageThresholdSupported()) {
+                    // In all collectors except G1, only the old generation supports a
+                    // usage threshold. The G1 legacy mode "G1 Old Gen" also does. In
+                    // G1 default mode, both the old space ("G1 Old Space": it's not
+                    // really a generation in the non-G1 collector sense) and the
+                    // humongous space ("G1 Humongous Space"), support a usage threshold.
+                    // So, the following condition is true for all non-G1 old generations,
+                    // for the G1 legacy old gen, and for the G1 default humongous space.
+                    // It is not true for the G1 default old gen.
+                    //
+                    // We're allocating humongous objects in this test, so the G1 default
+                    // mode "G1 Old Space" occupancy doesn't change, because humongous
+                    // objects are allocated in the "G1 Humongous Space". If we allowed
+                    // the G1 default mode "G1 Old Space", notification would never
+                    // happen because no objects are allocated there.
+                    if (!p.getName().equals("G1 Old Space")) {
                     found = true;
                     testPool(p);
                 }
             }
+            }
             if (!found) {
                 throw new RuntimeException("No heap pool found");
             }
         }
     }

@@ -129,17 +148,15 @@
                 formatSize("Before allocation: peak", peak0.getUsed()) +
                 " expected to be < " +
                 formatSize("After allocation: peak", peak1.getUsed()));
         }
 
-
-        // The object is now garbage and do a GC
-        // memory usage should drop
+        // The object is now garbage and do a GC. Memory usage should drop.
         obj = null;
 
-        //This will cause sure shot GC unlike Runtime.gc() invoked by mbean.gc()
-        while(weakRef.get() != null) {
+        // This will cause a sure shot GC unlike Runtime.gc() invoked by mbean.gc()
+        while (weakRef.get() != null) {
             mbean.gc();
         }
 
         MemoryUsage usage2 = mpool.getUsage();
         MemoryUsage peak2 = mpool.getPeakUsage();