8015272: Make @Contended within the same group to use the same oop map

Reviewed-by: coleenp, dholmes

hotspot/src/share/vm/classfile/classFileParser.cpp

@@ -3492,17 +3492,18 @@ void ClassFileParser::layout_fields(Handle class_loader,
           real_offset = next_nonstatic_oop_offset;
           next_nonstatic_oop_offset += heapOopSize;
         }
-        // Update oop maps
+
+        // Record this oop in the oop maps
         if( nonstatic_oop_map_count > 0 &&
             nonstatic_oop_offsets[nonstatic_oop_map_count - 1] ==
             real_offset -
             int(nonstatic_oop_counts[nonstatic_oop_map_count - 1]) *
             heapOopSize ) {
-          // Extend current oop map
+          // This oop is adjacent to the previous one, add to current oop map
           assert(nonstatic_oop_map_count - 1 < max_nonstatic_oop_maps, "range check");
           nonstatic_oop_counts[nonstatic_oop_map_count - 1] += 1;
         } else {
-          // Create new oop map
+          // This oop is not adjacent to the previous one, create new oop map
           assert(nonstatic_oop_map_count < max_nonstatic_oop_maps, "range check");
           nonstatic_oop_offsets[nonstatic_oop_map_count] = real_offset;
           nonstatic_oop_counts [nonstatic_oop_map_count] = 1;
@@ -3624,7 +3625,17 @@ void ClassFileParser::layout_fields(Handle class_loader,
             real_offset = next_nonstatic_padded_offset;
             next_nonstatic_padded_offset += heapOopSize;
 
-            // Create new oop map
+            // Record this oop in the oop maps
+            if( nonstatic_oop_map_count > 0 &&
+                nonstatic_oop_offsets[nonstatic_oop_map_count - 1] ==
+                real_offset -
+                int(nonstatic_oop_counts[nonstatic_oop_map_count - 1]) *
+                heapOopSize ) {
+              // This oop is adjacent to the previous one, add to current oop map
+              assert(nonstatic_oop_map_count - 1 < max_nonstatic_oop_maps, "range check");
+              nonstatic_oop_counts[nonstatic_oop_map_count - 1] += 1;
+            } else {
+              // This oop is not adjacent to the previous one, create new oop map
               assert(nonstatic_oop_map_count < max_nonstatic_oop_maps, "range check");
               nonstatic_oop_offsets[nonstatic_oop_map_count] = real_offset;
               nonstatic_oop_counts [nonstatic_oop_map_count] = 1;
@@ -3632,6 +3643,7 @@ void ClassFileParser::layout_fields(Handle class_loader,
               if( first_nonstatic_oop_offset == 0 ) { // Undefined
                 first_nonstatic_oop_offset = real_offset;
               }
+            }
             break;
 
           default:

hotspot/test/runtime/contended/OopMapsSameGroup.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.lang.Class;
+import java.lang.String;
+import java.lang.System;
+import java.lang.management.ManagementFactory;
+import java.lang.management.RuntimeMXBean;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CyclicBarrier;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import sun.misc.Unsafe;
+import sun.misc.Contended;
+
+/*
+ * @test
+ * @bug     8015272
+ * @summary \@Contended within the same group to use the same oop map
+ *
+ * @run main/othervm -XX:-RestrictContended -XX:ContendedPaddingWidth=128 -Xmx128m OopMapsSameGroup
+ */
+public class OopMapsSameGroup {
+
+    public static final int COUNT = 10000;
+
+    public static void main(String[] args) throws Exception {
+        Object o01 = new Object();
+        Object o02 = new Object();
+        Object o03 = new Object();
+        Object o04 = new Object();
+
+        R[] rs = new R[COUNT];
+
+        for (int i = 0; i < COUNT; i++) {
+           R r = new R();
+           r.o01 = o01;
+           r.o02 = o02;
+           r.o03 = o03;
+           r.o04 = o04;
+           rs[i] = r;
+        }
+
+        System.gc();
+
+        for (int i = 0; i < COUNT; i++) {
+           R r = rs[i];
+           if (r.o01 != o01) throw new Error("Test Error: o01");
+           if (r.o02 != o02) throw new Error("Test Error: o02");
+           if (r.o03 != o03) throw new Error("Test Error: o03");
+           if (r.o04 != o04) throw new Error("Test Error: o04");
+        }
+    }
+
+    public static class R {
+        @Contended("group1")
+        Object o01;
+
+        @Contended("group1")
+        Object o02;
+
+        @Contended("group2")
+        Object o03;
+
+        @Contended("group2")
+        Object o04;
+    }
+
+}
+