8249719: MethodHandle performance suffers from bad ResolvedMethodTable hash function

Reviewed-by: simonis, stuefe, coleenp

Author: Andrei Pangin

src/hotspot/share/prims/resolvedMethodTable.cpp

@@ -53,9 +53,10 @@ static const size_t GROW_HINT = 32;
 static const size_t ResolvedMethodTableSizeLog = 10;
 
 unsigned int method_hash(const Method* method) {
-  unsigned int name_hash = method->name()->identity_hash();
-  unsigned int signature_hash = method->signature()->identity_hash();
-  return name_hash ^ signature_hash;
+  unsigned int hash = method->klass_name()->identity_hash();
+  hash = (hash * 31) ^ method->name()->identity_hash();
+  hash = (hash * 31) ^ method->signature()->identity_hash();
+  return hash;
 }
 
 typedef ConcurrentHashTable<ResolvedMethodTableConfig,

test/hotspot/jtreg/runtime/MemberName/ResolvedMethodTableHash.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2020, 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.
+ */
+
+/*
+ * @test
+ * @bug 8249719
+ * @summary ResolvedMethodTable hash function should take method class into account
+ * @run main/othervm/manual -Xmx256m -XX:MaxMetaspaceSize=256m ResolvedMethodTableHash 200000
+ */
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+
+// The test generates thousands MethodHandles to the methods of the same name
+// and the same signature. This should not take too long, unless Method hash
+// function takes only the name and the signature as an input.
+public class ResolvedMethodTableHash extends ClassLoader {
+
+    // Generate a MethodHandle for ClassName.m()
+    private MethodHandle generate(String className) throws ReflectiveOperationException {
+        byte[] buf = new byte[100];
+        int size = writeClass(buf, className);
+        Class<?> cls = defineClass(null, buf, 0, size);
+        return MethodHandles.publicLookup().findStatic(cls, "m", MethodType.methodType(void.class));
+    }
+
+    // Produce a class file with the given name and a single method:
+    //     public static native void m();
+    private int writeClass(byte[] buf, String className) {
+        return ByteBuffer.wrap(buf)
+                .putInt(0xCAFEBABE)       // magic
+                .putInt(50)               // version: 50
+                .putShort((short) 7)      // constant_pool_count: 7
+                .put((byte) 7).putShort((short) 2)
+                .put((byte) 1).putShort((short) className.length()).put(className.getBytes())
+                .put((byte) 7).putShort((short) 4)
+                .put((byte) 1).putShort((short) 16).put("java/lang/Object".getBytes())
+                .put((byte) 1).putShort((short) 1).put("m".getBytes())
+                .put((byte) 1).putShort((short) 3).put("()V".getBytes())
+                .putShort((short) 0x21)   // access_flags: public super
+                .putShort((short) 1)      // this_class: #1
+                .putShort((short) 3)      // super_class: #3
+                .putShort((short) 0)      // interfaces_count: 0
+                .putShort((short) 0)      // fields_count: 0
+                .putShort((short) 1)      // methods_count: 1
+                .putShort((short) 0x109)  //   access_flags: public static native
+                .putShort((short) 5)      //   name_index: #5
+                .putShort((short) 6)      //   descriptor_index: #6
+                .putShort((short) 0)      //   attributes_count: 0
+                .putShort((short) 0)      // attributes_count: 0
+                .position();
+    }
+
+    public static void main(String[] args) throws Exception {
+        ResolvedMethodTableHash generator = new ResolvedMethodTableHash();
+        List<MethodHandle> handles = new ArrayList<>();
+
+        int count = args.length > 0 ? Integer.parseInt(args[0]) : 200000;
+
+        for (int i = 0; i < count; i++) {
+            handles.add(generator.generate("MH$" + i));
+            if (i % 1000 == 0) {
+                System.out.println("Generated " + i + " handles");
+            }
+        }
+
+        System.out.println("Test passed");
+    }
+}