Android: lazy initialization for method id.

base/android/jni_android_unittest.cc

Index: base/android/jni_android_unittest.cc
diff --git a/base/android/jni_android_unittest.cc b/base/android/jni_android_unittest.cc
index abecad778b47c72830d1e0a3345f6cf7c1d05140..79006a50cfb9caef6d850f6ca2961c4468a08380 100644
--- a/base/android/jni_android_unittest.cc
+++ b/base/android/jni_android_unittest.cc
@@ -33,6 +33,24 @@ jmethodID GetMethodIDWrapper(JNIEnv* env, jclass clazz, const char* method,
   return g_last_method_id;
 }
 
+
+static jmethodID g_MTCall = 0;
+jobject MTCall(JNIEnv* env, jclass clazz, int p) {
+  base::android::LazyMethodID::Get<
+      base::android::LazyMethodID::METHODTYPE_STATIC,
+      base::android::LazyMethodID::EXCEPTIONCHECK_NO>(
+      env, clazz,
+      "valueOf",
+      "(I)Ljava/lang/String;",
+      &g_MTCall);
+
+  return env->CallStaticObjectMethod(clazz, g_MTCall, p);
+}
+
+jobject NonMTCall(JNIEnv* env, jclass clazz, int p) {
+  return env->CallStaticObjectMethod(clazz, g_MTCall, p);
+}
+
 }  // namespace
 
 class JNIAndroidTest : public testing::Test {
@@ -90,5 +108,24 @@ TEST_F(JNIAndroidTest, GetMethodIDFromClassNameCaching) {
   EXPECT_EQ(g_last_method_id, id3);
 }
 
+TEST(JNIAndroidMicrobenchmark, JNIWithLock) {
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jclass> clazz(GetClass(env, "java/lang/String"));
+  base::Time start_mt = base::Time::Now();
+  for (int i = 0; i < 1024; ++i)
+    ScopedJavaLocalRef<jobject> o(env, MTCall(env, clazz.obj(), i));
+  base::Time end_mt = base::Time::Now();
+
+  base::Time start_non_mt = base::Time::Now();
+  for (int i = 0; i < 1024; ++i)
+    ScopedJavaLocalRef<jobject> o(env, NonMTCall(env, clazz.obj(), i));
+  base::Time end_non_mt = base::Time::Now();
+
+  LOG(ERROR) << "JNI MT" <<
+      base::TimeDelta(start_mt - end_mt).InMicroseconds();
+  LOG(ERROR) << "JNI Non-MT" <<
+      base::TimeDelta(start_non_mt - end_non_mt).InMicroseconds();
+}
+
 }  // namespace android
 }  // namespace base