1 files changed, 95 insertions, 0 deletions
diff --git a/api/src/jmh/java/io/perfmark/ClassInitBenchmark.java b/api/src/jmh/java/io/perfmark/ClassInitBenchmark.java
new file mode 100644
index 0000000..0944b41
--- /dev/null
+++ b/api/src/jmh/java/io/perfmark/ClassInitBenchmark.java
@@ -0,0 +1,95 @@
+/*
+ * Copyright 2021 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.perfmark;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+@State(Scope.Benchmark)
+@Fork(1000)
+@Warmup(iterations = 0)
+@Measurement(iterations = 1)
+public class ClassInitBenchmark {
+
+  private ClassLoader loader;
+
+  @Setup
+  public void setup() {
+    loader = new TestClassLoader(getClass().getClassLoader(), "io.perfmark.impl.SecretPerfMarkImpl$PerfMarkImpl");
+  }
+
+  @Benchmark
+  @BenchmarkMode(Mode.SingleShotTime)
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
+  public Object forName_noinit() throws Exception {
+    return Class.forName(PerfMark.class.getName(), false, loader);
+  }
+
+  @Benchmark
+  @BenchmarkMode(Mode.SingleShotTime)
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
+  public Object forName_init() throws Exception {
+    return Class.forName(PerfMark.class.getName(), true, loader);
+  }
+
+  private static class TestClassLoader extends ClassLoader {
+
+    private final List<String> classesToDrop;
+
+    TestClassLoader(ClassLoader parent, String ... classesToDrop) {
+      super(parent);
+      this.classesToDrop = Arrays.asList(classesToDrop);
+    }
+
+    @Override
+    protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
+      if (classesToDrop.contains(name)) {
+        // Throw an exception, just like the real one would.
+        throw new ClassNotFoundException();
+      }
+      if (!name.startsWith("io.perfmark.")) {
+        return super.loadClass(name, resolve);
+      }
+      try (InputStream is = getParent().getResourceAsStream(name.replace('.', '/') + ".class")) {
+        if (is == null) {
+          throw new ClassNotFoundException(name);
+        }
+        byte[] data = is.readAllBytes();
+        Class<?> clz = defineClass(name, data, 0, data.length);
+        if (resolve) {
+          resolveClass(clz);
+        }
+        return clz;
+      } catch (IOException e) {
+        throw new RuntimeException(e);
+      }
+    }
+  }
+}