8355233: Add a DMB related benchmark

Reviewed-by: kvn

Author: Eric Caspole

test/micro/org/openjdk/bench/vm/compiler/DMBCheck.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2025, 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.
+ */
+
+package org.openjdk.bench.vm.compiler;
+
+import java.util.concurrent.TimeUnit;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.CompilerControl;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Group;
+import org.openjdk.jmh.annotations.GroupThreads;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OperationsPerInvocation;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+@BenchmarkMode(Mode.Throughput)
+@State(Scope.Benchmark)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+@Warmup(iterations = 8, time = 4)
+@Measurement(iterations = 6, time = 3)
+public class DMBCheck {
+
+  // The allocations of DoubleDMB$A and DoubleDMB$C
+  // will cause aarch64 dmb barrier instructions.
+  // The different latency of the dmb ish/ishst/ishld modes
+  // may make a noticeable difference in the benchmark results.
+  // These modes may be set by cpu defaults or XX options.
+
+  class A {
+
+    final String b = new String("Hi there");
+  }
+
+  class C {
+
+    private A a;
+
+    public A getA() {
+      if (a == null) {
+        a = new A();
+      }
+      return a;
+    }
+  }
+
+  static C c = null;
+
+  @Setup
+  public void setup() {
+    c = new C();
+  }
+
+  @CompilerControl(CompilerControl.Mode.DONT_INLINE)
+  void action(Blackhole b) throws Exception {
+    c = new C();
+
+    if (c.getA().b == null) {
+      throw new Exception("a should not be null");
+    }
+    b.consume(c);
+  }
+
+  @Benchmark
+  @Fork(value = 1, jvmArgs = {
+    "-XX:+UnlockDiagnosticVMOptions", "-XX:+AlwaysMergeDMB", "-XX:+IgnoreUnrecognizedVMOptions"})
+  public void plusAlwaysMergeDMB(Blackhole b) throws Exception {
+
+    action(b);
+  }
+
+  @Benchmark
+  @Fork(value = 1, jvmArgs = {
+    "-XX:+UnlockDiagnosticVMOptions", "-XX:-AlwaysMergeDMB", "-XX:+IgnoreUnrecognizedVMOptions"})
+  public void minusAlwaysMergeDMB(Blackhole b) throws Exception {
+
+    action(b);
+  }
+
+}