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LockCoarseningBenchmark.java
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LockCoarseningBenchmark.java
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/*
* JVM Performance Benchmarks
*
* Copyright (C) 2019 - 2024 Ionut Balosin
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 com.ionutbalosin.jvm.performance.benchmarks.compiler;
import java.util.Random;
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;
/*
* Test how the compiler can effectively coarsen/merge several adjacent synchronized blocks into one synchronized block,
* thus reducing the locking overhead. This optimization can be applied if the same lock object is used by all methods.
* Compilers can help to coarsen/merge the locks, but that is not guaranteed.
*
* OpenJDK HotSpot VM specifics:
* - prior JDK 15: with biased locking enabled, compare-and-swap atomic operation are basically no-ops when acquiring a monitor, in case of uncontended locking.
* It assumes that a monitor remains owned by a given thread until a different thread tries to acquire it
* - starting JDK 15: without biased locking (or some improved version of non-biased locking), in case of uncontended locking,
* certain synchronized scenarios might become slightly slower (i.e., since synchronized calls come now with atomic compare-and-swap on lock)
*
* ZGC and Shenandoah GC have biased locking disabled to prevent safepoint operations (e.g., biased locking revocation), avoiding stop-the-world pauses.
*
* References:
* - https://openjdk.org/jeps/374
*/
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 5, time = 10, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 5, time = 10, timeUnit = TimeUnit.SECONDS)
@Fork(value = 5)
@State(Scope.Benchmark)
public class LockCoarseningBenchmark {
// $ java -jar */*/benchmarks.jar ".*LockCoarseningBenchmark.*"
// Recommended command line options only for JDK 17:
// - JVM options: {-XX:-UseBiasedLocking, -XX:+UseBiasedLocking}
private final Random random = new Random(16384);
private final int DEPTH = 8;
private int defaultValue;
private int incrementValue;
@Setup
public void setup() {
defaultValue = 32 + random.nextInt(64);
incrementValue = random.nextInt(32);
}
@Benchmark
public int nested_synchronized() {
int result = defaultValue << 1;
synchronized (this) {
result += incrementValue;
synchronized (this) {
result += incrementValue;
synchronized (this) {
result += incrementValue;
synchronized (this) {
result += incrementValue;
synchronized (this) {
result += incrementValue;
synchronized (this) {
result += incrementValue;
synchronized (this) {
result += incrementValue;
synchronized (this) {
result += incrementValue;
}
}
}
}
}
}
}
}
return result;
}
@Benchmark
public int recursive_method_calls() {
int result = defaultValue << 1;
result = recursiveSum(result, DEPTH);
return result;
}
@Benchmark
public int chain_method_calls() {
int result = defaultValue << 1;
result = sum(result);
result = sum(result);
result = sum(result);
result = sum(result);
result = sum(result);
result = sum(result);
result = sum(result);
result = sum(result);
return result;
}
@Benchmark
public int conditional_chain_method_calls() {
int result = defaultValue << 1;
// all conditionals are evaluated to "true"
if (result > 1 << 5) {
result = sum(result);
}
if (result > 1 << 5) {
result = sum(result);
}
if (result > 1 << 5) {
result = sum(result);
}
if (result > 1 << 5) {
result = sum(result);
}
if (result > 1 << 5) {
result = sum(result);
}
if (result > 1 << 5) {
result = sum(result);
}
if (result > 1 << 5) {
result = sum(result);
}
if (result > 1 << 5) {
result = sum(result);
}
return result;
}
@Benchmark
public int conditional_nested_method_calls() {
int result = defaultValue << 1;
// all conditionals are evaluated to "true"
if (result > 1 << 5) {
result = sum(result);
if (result > 1 << 5) {
result = sum(result);
if (result > 1 << 5) {
result = sum(result);
if (result > 1 << 5) {
result = sum(result);
if (result > 1 << 5) {
result = sum(result);
if (result > 1 << 5) {
result = sum(result);
if (result > 1 << 5) {
result = sum(result);
if (result > 1 << 5) {
result = sum(result);
}
}
}
}
}
}
}
}
return result;
}
@Benchmark
public int baseline() {
int result = defaultValue << 1;
synchronized (this) {
result += incrementValue;
result += incrementValue;
result += incrementValue;
result += incrementValue;
result += incrementValue;
result += incrementValue;
result += incrementValue;
result += incrementValue;
}
return result;
}
public synchronized int sum(int aValue) {
return aValue + incrementValue;
}
public synchronized int recursiveSum(int aValue, int depth) {
if (depth == 0) {
return aValue;
}
return incrementValue + recursiveSum(aValue, depth - 1);
}
}