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JVM性能调优实战手册：从基础原理到生产实践

news 2025/11/17 13:08:12

引言

JVM性能调优是Java开发者必须掌握的核心技能。面对生产环境中的性能问题，你是否曾感到无从下手？本文将带你从JVM基础原理出发，通过实战案例深入掌握性能调优的完整方法论，构建系统的性能优化思维。

JVM内存模型深度解析

1.1 运行时数据区详解

public class MemoryLayoutDemo {// 类变量 - 方法区private static final String CLASS_CONSTANT = "常量池";private static int staticCounter = 0;// 实例变量 - 堆内存private int instanceId;private String instanceName;public void demonstrateMemoryAreas() {// 局部变量 - 栈帧中的局部变量表int localVar = 42;String localString = "栈上的引用";// 数组对象 - 堆内存int[] array = new int[1000];// 方法调用 - 创建新的栈帧recursiveMethod(5);// 线程局部变量ThreadLocal<String> threadLocal = new ThreadLocal<>();threadLocal.set("线程隔离的数据");}private void recursiveMethod(int depth) {// 每次递归调用都会创建新的栈帧if (depth > 0) {int localDepth = depth; // 每个栈帧有自己的局部变量recursiveMethod(depth - 1);}}// 演示对象内存布局public static class ObjectLayout {private boolean flag;      // 1字节private byte b;           // 1字节  private char c;           // 2字节private short s;          // 2字节private int i;            // 4字节private long l;           // 8字节private double d;         // 8字节private Object ref;       // 4/8字节（32/64位）// 数组对象有额外的数组长度字段private int[] array = new int[10];}// 使用JOL（Java Object Layout）分析对象内存布局public void analyzeObjectLayout() {/** 添加依赖：* <dependency>*     <groupId>org.openjdk.jol</groupId>*     <artifactId>jol-core</artifactId>*     <version>0.17</version>* </dependency>*/try {// 使用反射获取JOL类Class<?> jolClass = Class.forName("org.openjdk.jol.vm.VM");Object vm = jolClass.getMethod("current").invoke(null);System.out.println("对象对齐: " + jolClass.getMethod("objectAlignment").invoke(vm));} catch (Exception e) {System.out.println("请添加JOL依赖以获取详细对象布局信息");}}
}

1.2 内存分配机制

public class MemoryAllocationDemo {// 对象分配过程演示public void objectAllocationProcess() {// 大多数对象在Eden区分配for (int i = 0; i < 100000; i++) {// 小对象直接在TLAB（Thread Local Allocation Buffer）分配SmallObject obj = new SmallObject(i, "obj-" + i);if (i % 1000 == 0) {// 模拟大对象直接进入老年代LargeObject large = new LargeObject(new byte[1024 * 1024]); // 1MB}}}static class SmallObject {private int id;private String name;private byte[] data = new byte[1024]; // 1KBpublic SmallObject(int id, String name) {this.id = id;this.name = name;}}static class LargeObject {private byte[] largeData;public LargeObject(byte[] data) {this.largeData = data;}}// 逃逸分析优化演示public void escapeAnalysisDemo() {// 这个对象不会逃逸出方法，可能被栈上分配或标量替换for (int i = 0; i < 1000000; i++) {NonEscapingObject obj = new NonEscapingObject(i);obj.doSomething();}}static class NonEscapingObject {private int value;public NonEscapingObject(int value) {this.value = value;}public void doSomething() {// 简单的计算，对象不会逃逸value = value * 2;}}// 内存分配失败监控public void monitorAllocationFailure() {Runtime runtime = Runtime.getRuntime();long allocatedMemory = runtime.totalMemory() - runtime.freeMemory();long maxMemory = runtime.maxMemory();System.out.printf("已分配内存: %.2fMB%n", allocatedMemory / 1024.0 / 1024.0);System.out.printf("最大内存: %.2fMB%n", maxMemory / 1024.0 / 1024.0);System.out.printf("使用率: %.2f%%%n", allocatedMemory * 100.0 / maxMemory);if (allocatedMemory > maxMemory * 0.9) {System.out.println("警告: 内存使用率超过90%!");}}
}

垃圾回收算法与调优

2.1 GC算法深度解析

public class GCAlgorithmAnalysis {// 引用类型演示public void referenceTypesDemo() {// 强引用 - 不会被GC回收Object strongRef = new Object();// 软引用 - 内存不足时回收SoftReference<byte[]> softRef = new SoftReference<>(new byte[1024 * 1024]);// 弱引用 - 下次GC时回收WeakReference<Object> weakRef = new WeakReference<>(new Object());// 虚引用 - 主要用于跟踪对象被回收的状态ReferenceQueue<Object> queue = new ReferenceQueue<>();PhantomReference<Object> phantomRef = new PhantomReference<>(new Object(), queue);// 验证引用类型的行为System.gc();System.out.println("强引用: " + (strongRef != null));System.out.println("软引用: " + (softRef.get() != null));System.out.println("弱引用: " + (weakRef.get() != null));System.out.println("虚引用: " + (phantomRef.get() != null));}// 垃圾回收日志分析public static class GCLogAnalyzer {/*** GC日志配置示例:* -Xlog:gc*:file=gc.log:time,uptime,level,tags:filecount=10,filesize=100m* -XX:+PrintGCDetails -XX:+PrintGCDateStamps*/public void analyzeGCLog(String logContent) {// 解析GC日志的简单示例String[] lines = logContent.split("\n");for (String line : lines) {if (line.contains("GC") || line.contains("Full GC")) {parseGCLine(line);}}}private void parseGCLine(String line) {// 简化的GC日志解析if (line.contains("Pause Young")) {System.out.println("年轻代GC: " + line);} else if (line.contains("Pause Full")) {System.out.println("Full GC: " + line);} else if (line.contains("Allocation Failure")) {System.out.println("分配失败触发GC: " + line);}}}// 对象生命周期跟踪public static class ObjectLifecycleTracker {private final Map<String, ObjectCreationInfo> objectMap = new WeakHashMap<>();public void trackObjectCreation(Object obj, String description) {objectMap.put(System.identityHashCode(obj) + "-" + description, new ObjectCreationInfo(obj, description, System.currentTimeMillis()));}public void printSurvivingObjects() {long currentTime = System.currentTimeMillis();System.out.println("=== 存活对象统计 ===");objectMap.entrySet().removeIf(entry -> {ObjectCreationInfo info = entry.getValue();if (info.getObject() == null) {return true; // 已被GC回收}long age = currentTime - info.getCreationTime();System.out.printf("对象: %s, 年龄: %dms%n", info.getDescription(), age);return false;});}}static class ObjectCreationInfo {private final WeakReference<Object> objectRef;private final String description;private final long creationTime;public ObjectCreationInfo(Object obj, String desc, long time) {this.objectRef = new WeakReference<>(obj);this.description = desc;this.creationTime = time;}public Object getObject() { return objectRef.get(); }public String getDescription() { return description; }public long getCreationTime() { return creationTime; }}
}

2.2 垃圾收集器实战配置

public class GarbageCollectorTuning {// G1GC调优配置public static class G1GCTuning {/*** G1GC生产环境推荐配置:* -XX:+UseG1GC* -Xms4g -Xmx4g                    # 堆大小固定* -XX:MaxGCPauseMillis=200         # 目标暂停时间* -XX:G1HeapRegionSize=16m         # Region大小* -XX:G1NewSizePercent=30          # 年轻代最小占比* -XX:G1MaxNewSizePercent=60       # 年轻代最大占比* -XX:InitiatingHeapOccupancyPercent=45  # 并发周期触发阈值* -XX:ConcGCThreads=4              # 并发GC线程数*/public void monitorG1GC() {List<GarbageCollectorMXBean> gcBeans = ManagementFactory.getGarbageCollectorMXBeans();for (GarbageCollectorMXBean gcBean : gcBeans) {System.out.println("GC: " + gcBean.getName());System.out.println("  收集次数: " + gcBean.getCollectionCount());System.out.println("  收集时间: " + gcBean.getCollectionTime() + "ms");// G1GC特定指标if (gcBean.getName().contains("G1")) {printG1SpecificMetrics();}}}private void printG1SpecificMetrics() {// 获取G1GC特定指标（需要通过JMX）try {MBeanServer mBeanServer = ManagementFactory.getPlatformMBeanServer();// G1GC的JMX Bean名称ObjectName g1Bean = new ObjectName("java.lang:type=GarbageCollector,name=G1*");// 可以获取更多G1GC特定指标System.out.println("  G1GC Young Generation Metrics available via JMX");} catch (Exception e) {System.out.println("  无法获取G1GC详细指标: " + e.getMessage());}}}// ZGC调优配置public static class ZGCTuning {/*** ZGC生产环境推荐配置:* -XX:+UseZGC* -XX:+ZGenerational               # Java 21+ 启用分代ZGC* -Xms4g -Xmx4g                    # 堆大小* -XX:SoftMaxHeapSize=3g           # 堆软限制* -XX:ZCollectionInterval=300      # 收集间隔(秒)* -XX:ZAllocationSpikeTolerance=2  # 分配峰值容忍度* -Xlog:gc*,gc+heap=info:file=gc.log*/public void zgcPerformanceTest() {// ZGC性能测试场景long startTime = System.currentTimeMillis();// 创建大量短期对象List<byte[]> shortLivedObjects = new ArrayList<>();for (int i = 0; i < 100000; i++) {shortLivedObjects.add(new byte[1024]); // 1KB对象if (i % 1000 == 0) {// 定期清理，模拟对象生命周期shortLivedObjects.clear();System.gc(); // 提示GC}}// 创建长期存活对象List<byte[]> longLivedObjects = new ArrayList<>();for (int i = 0; i < 1000; i++) {longLivedObjects.add(new byte[1024 * 1024]); // 1MB对象}long duration = System.currentTimeMillis() - startTime;System.out.println("ZGC测试完成，耗时: " + duration + "ms");}}// Shenandoah GC调优public static class ShenandoahTuning {/*** Shenandoah GC配置:* -XX:+UseShenandoahGC* -Xms2g -Xmx2g* -XX:ShenandoahGCHeuristics=adaptive   # 启发式策略* -XX:ShenandoahGCMode=iu              # 增量更新模式* -XX:ShenandoahTargetIntervalMs=100   # 目标间隔*/}// GC选择决策树public String recommendGC(long heapSize, long maxPauseTime, boolean throughputFirst) {if (heapSize <= 8 * 1024 * 1024 * 1024L) { // 8GB以下if (maxPauseTime < 100) {return "ZGC (低延迟需求)";} else if (throughputFirst) {return "G1GC (吞吐量优先)";} else {return "ShenandoahGC (平衡型)";}} else {// 大堆应用if (maxPauseTime < 200) {return "ZGC";} else {return "G1GC";}}}
}

性能监控与诊断工具

3.1 内置工具使用

public class BuiltInMonitoringTools {// JVM基础监控public void monitorBasicJVMStats() {Runtime runtime = Runtime.getRuntime();MemoryMXBean memoryBean = ManagementFactory.getMemoryMXBean();ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();OperatingSystemMXBean osBean = ManagementFactory.getOperatingSystemMXBean();// 内存监控MemoryUsage heapUsage = memoryBean.getHeapMemoryUsage();MemoryUsage nonHeapUsage = memoryBean.getNonHeapMemoryUsage();System.out.println("=== JVM监控数据 ===");System.out.printf("堆内存: %d / %d MB (%.1f%%)%n",heapUsage.getUsed() / 1024 / 1024,heapUsage.getMax() / 1024 / 1024,heapUsage.getUsed() * 100.0 / heapUsage.getMax());System.out.printf("非堆内存: %d / %d MB%n",nonHeapUsage.getUsed() / 1024 / 1024,nonHeapUsage.getMax() / 1024 / 1024);// 线程监控System.out.printf("活动线程: %d, 峰值: %d%n",threadBean.getThreadCount(),threadBean.getPeakThreadCount());// CPU监控System.out.printf("系统负载: %.2f, 可用CPU: %d%n",osBean.getSystemLoadAverage(),runtime.availableProcessors());// GC监控List<GarbageCollectorMXBean> gcBeans = ManagementFactory.getGarbageCollectorMXBeans();for (GarbageCollectorMXBean gcBean : gcBeans) {System.out.printf("GC %s: 次数=%d, 时间=%dms%n",gcBean.getName(), gcBean.getCollectionCount(), gcBean.getCollectionTime());}}// 详细的线程分析public void analyzeThreads() {ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();// 获取所有线程IDlong[] threadIds = threadBean.getAllThreadIds();System.out.println("=== 线程详细分析 ===");for (long threadId : threadIds) {ThreadInfo threadInfo = threadBean.getThreadInfo(threadId);if (threadInfo != null) {System.out.printf("线程[%d] %s: %s%n",threadId,threadInfo.getThreadName(),threadInfo.getThreadState());// 显示锁信息if (threadInfo.getLockName() != null) {System.out.printf("  等待锁: %s, 拥有者: %s%n",threadInfo.getLockName(),threadInfo.getLockOwnerName());}// 显示CPU时间if (threadBean.isThreadCpuTimeSupported()) {long cpuTime = threadBean.getThreadCpuTime(threadId);long userTime = threadBean.getThreadUserTime(threadId);System.out.printf("  CPU时间: %dms, 用户时间: %dms%n",cpuTime / 1000000, userTime / 1000000);}}}}// 内存池详细监控public void monitorMemoryPools() {List<MemoryPoolMXBean> memoryPools = ManagementFactory.getMemoryPoolMXBeans();System.out.println("=== 内存池详情 ===");for (MemoryPoolMXBean pool : memoryPools) {MemoryUsage usage = pool.getUsage();MemoryUsage peakUsage = pool.getPeakUsage();System.out.printf("内存池: %s%n", pool.getName());System.out.printf("  类型: %s%n", pool.getType());System.out.printf("  使用: %d / %d MB%n",usage.getUsed() / 1024 / 1024,usage.getMax() / 1024 / 1024);System.out.printf("  峰值: %d MB%n",peakUsage.getUsed() / 1024 / 1024);// GC相关信息if (pool.isUsageThresholdSupported()) {System.out.printf("  使用率阈值: %.1f%%%n",pool.getUsageThreshold() * 100.0 / usage.getMax());}}}
}

3.2 第三方工具集成

public class ThirdPartyMonitoringTools {// Micrometer指标收集public static class MicrometerIntegration {private final MeterRegistry meterRegistry;public MicrometerIntegration(MeterRegistry registry) {this.meterRegistry = registry;initializeMetrics();}private void initializeMetrics() {// JVM内存指标new JvmMemoryMetrics().bindTo(meterRegistry);// GC指标new JvmGcMetrics().bindTo(meterRegistry);// 线程指标new JvmThreadMetrics().bindTo(meterRegistry);// 自定义业务指标Counter.builder("jvm.gc.count").description("GC次数").register(meterRegistry);Gauge.builder("jvm.memory.used").description("已用内存").register(meterRegistry, this, self -> {Runtime runtime = Runtime.getRuntime();return runtime.totalMemory() - runtime.freeMemory();});}public void recordBusinessMetric(String operation, long duration) {Timer.builder("business.operation").tag("operation", operation).register(meterRegistry).record(duration, TimeUnit.MILLISECONDS);}}// Arthas集成示例public static class ArthasIntegration {/*** Arthas常用命令:* dashboard    - 实时监控面板* thread       - 线程状态查看* jvm          - JVM信息* monitor      - 方法执行监控* watch        - 方法执行数据观测* trace        - 方法内部调用路径* ognl         - 执行ognl表达式*/public void simulateArthasCommands() {System.out.println("=== Arthas 模拟命令 ===");System.out.println("1. 查看最忙的线程:");printBusiestThreads();System.out.println("2. 监控方法执行:");monitorMethodExecution();System.out.println("3. 内存对象统计:");analyzeMemoryObjects();}private void printBusiestThreads() {ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();long[] threadIds = threadBean.getAllThreadIds();// 按CPU时间排序Arrays.stream(threadIds).mapToObj(threadBean::getThreadInfo).filter(Objects::nonNull).sorted((t1, t2) -> Long.compare(threadBean.getThreadCpuTime(t2.getThreadId()),threadBean.getThreadCpuTime(t1.getThreadId()))).limit(5).forEach(info -> {long cpuTime = threadBean.getThreadCpuTime(info.getThreadId());System.out.printf("  %s (ID: %d) - CPU: %dms%n",info.getThreadName(), info.getThreadId(), cpuTime / 1000000);});}private void monitorMethodExecution() {// 模拟方法执行监控long startTime = System.currentTimeMillis();// 监控的方法monitoredMethod();long duration = System.currentTimeMillis() - startTime;System.out.printf("  方法执行时间: %dms%n", duration);}private void monitoredMethod() {try {Thread.sleep(100);// 模拟一些工作for (int i = 0; i < 1000; i++) {Math.sqrt(i);}} catch (InterruptedException e) {Thread.currentThread().interrupt();}}private void analyzeMemoryObjects() {// 简单的对象统计System.out.println("  对象类型统计:");System.gc();// 这里可以集成真正的内存分析工具System.out.println("  请使用Arthas的memory命令获取详细统计");}}
}

实战调优案例

4.1 内存泄漏诊断

public class MemoryLeakDiagnosis {// 常见内存泄漏模式public static class CommonMemoryLeaks {// 1. 静态集合引起的内存泄漏private static final Map<String, Object> staticCache = new HashMap<>();public void staticCollectionLeak() {// 对象被静态集合引用，无法被GC回收for (int i = 0; i < 100000; i++) {String key = "key-" + i;byte[] data = new byte[1024 * 1024]; // 1MBstaticCache.put(key, data);}}// 2. 未关闭的资源public void unclosedResources() {List<Connection> connections = new ArrayList<>();try {for (int i = 0; i < 100; i++) {// 模拟数据库连接Connection conn = new Connection("db-" + i);connections.add(conn);// 忘记调用 conn.close()}} catch (Exception e) {e.printStackTrace();}// connections 超出作用域，但Connection对象仍持有资源}// 3. 监听器未取消注册private final List<EventListener> listeners = new ArrayList<>();public void registerListener(EventListener listener) {listeners.add(listener);}// 缺少取消注册的方法，导致监听器无法被GC回收// 4. 内部类引用外部类public void innerClassReference() {for (int i = 0; i < 1000; i++) {// 匿名内部类隐式持有外部类引用new Thread(new Runnable() {@Overridepublic void run() {// 这里可以访问外部类的成员变量System.out.println("Processing...");}}).start();}}}// 内存泄漏检测工具public static class MemoryLeakDetector {private final Runtime runtime = Runtime.getRuntime();private long lastMemory = 0;private long increasingCount = 0;public void startMonitoring() {Thread monitorThread = new Thread(() -> {while (!Thread.currentThread().isInterrupted()) {try {checkMemoryUsage();Thread.sleep(5000); // 每5秒检查一次} catch (InterruptedException e) {Thread.currentThread().interrupt();}}});monitorThread.setDaemon(true);monitorThread.start();}private void checkMemoryUsage() {long currentMemory = runtime.totalMemory() - runtime.freeMemory();if (currentMemory > lastMemory) {increasingCount++;System.out.printf("内存持续增长: %d次, 当前: %.2fMB%n",increasingCount, currentMemory / 1024.0 / 1024.0);if (increasingCount > 10) {System.out.println("警告: 检测到可能的内存泄漏!");suggestActions();}} else {increasingCount = 0;}lastMemory = currentMemory;}private void suggestActions() {System.out.println("建议操作:");System.out.println("1. 生成堆转储: jmap -dump:live,format=b,file=heap.hprof <pid>");System.out.println("2. 分析大对象: jmap -histo:live <pid> | head -20");System.out.println("3. 使用MAT或JProfiler分析堆转储");}// 生成堆转储public void generateHeapDump() {String fileName = "heap-dump-" + System.currentTimeMillis() + ".hprof";try {HotSpotDiagnosticMXBean bean = ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class);bean.dumpHeap(fileName, true);System.out.println("堆转储已生成: " + fileName);} catch (IOException e) {System.err.println("生成堆转储失败: " + e.getMessage());}}}// 模拟连接类static class Connection implements AutoCloseable {private final String name;private final byte[] data = new byte[1024 * 1024]; // 模拟资源public Connection(String name) {this.name = name;System.out.println("创建连接: " + name);}@Overridepublic void close() {System.out.println("关闭连接: " + name);}}// 模拟事件监听器interface EventListener {void onEvent(String event);}
}

4.2 CPU性能优化

public class CPUPerformanceOptimization {// CPU使用率监控public void monitorCPUUsage() {ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();OperatingSystemMXBean osBean = ManagementFactory.getOperatingSystemMXBean();System.out.println("=== CPU监控 ===");System.out.printf("系统负载: %.2f%n", osBean.getSystemLoadAverage());System.out.printf("可用处理器: %d%n", Runtime.getRuntime().availableProcessors());// 线程级CPU监控long[] threadIds = threadBean.getAllThreadIds();for (long threadId : threadIds) {ThreadInfo info = threadBean.getThreadInfo(threadId);if (info != null && threadBean.getThreadCpuTime(threadId) > 1000000000L) { // 1秒以上System.out.printf("高CPU线程: %s (ID: %d)%n",info.getThreadName(), threadId);}}}// 热点方法识别public void identifyHotMethods() {long startTime = System.currentTimeMillis();// 模拟业务方法调用for (int i = 0; i < 1000000; i++) {if (i % 3 == 0) {expensiveMethod1();} else if (i % 3 == 1) {expensiveMethod2();} else {cheapMethod();}}long totalTime = System.currentTimeMillis() - startTime;System.out.println("总执行时间: " + totalTime + "ms");}private void expensiveMethod1() {// 模拟耗时操作long result = 0;for (int i = 0; i < 1000; i++) {result += Math.pow(i, 2);}}private void expensiveMethod2() {// 另一个耗时操作List<Double> numbers = new ArrayList<>();for (int i = 0; i < 500; i++) {numbers.add(Math.sqrt(i) * Math.log(i + 1));}numbers.sort(Double::compare);}private void cheapMethod() {// 快速操作// 空实现或简单计算}// 锁竞争优化public static class LockOptimization {private final Object heavyLock = new Object();private final AtomicLong counter = new AtomicLong();private final StampedLock stampedLock = new StampedLock();// 优化前：粗粒度锁public void processWithHeavyLock() {synchronized (heavyLock) {// 模拟一些工作try {Thread.sleep(10);} catch (InterruptedException e) {Thread.currentThread().interrupt();}counter.incrementAndGet();}}// 优化后：细粒度锁或无锁public void processOptimized() {// 使用原子操作避免锁long newValue = counter.incrementAndGet();// 只有需要同步的小部分代码使用锁if (newValue % 100 == 0) {synchronized (heavyLock) {// 批量处理或状态更新System.out.println("计数达到: " + newValue);}}}// 使用StampedLock优化读多写少场景public String readWithStampedLock() {long stamp = stampedLock.tryOptimisticRead();String data = readData();if (!stampedLock.validate(stamp)) {// 乐观读失败，升级为悲观读stamp = stampedLock.readLock();try {data = readData();} finally {stampedLock.unlockRead(stamp);}}return data;}private String readData() {return "data-" + counter.get();}}// 算法优化示例public static class AlgorithmOptimization {// 优化前：O(n²)算法public int findDuplicateNaive(int[] nums) {for (int i = 0; i < nums.length; i++) {for (int j = i + 1; j < nums.length; j++) {if (nums[i] == nums[j]) {return nums[i];}}}return -1;}// 优化后：O(n)算法public int findDuplicateOptimized(int[] nums) {Set<Integer> seen = new HashSet<>();for (int num : nums) {if (!seen.add(num)) {return num;}}return -1;}// 进一步优化：使用数组代替HashSetpublic int findDuplicateBest(int[] nums) {boolean[] visited = new boolean[nums.length];for (int num : nums) {if (visited[num]) {return num;}visited[num] = true;}return -1;}}
}

生产环境调优清单

5.1 调优检查表

public class ProductionTuningChecklist {public void performPreFlightCheck() {System.out.println("=== 生产环境调优检查表 ===");checkMemorySettings();checkGCSettings();checkJITSettings();checkMonitoringSettings();checkSecuritySettings();}private void checkMemorySettings() {Runtime runtime = Runtime.getRuntime();long maxMemory = runtime.maxMemory();System.out.println("1. 内存设置检查:");System.out.printf("  - 最大堆内存: %.2fGB%n", maxMemory / 1024.0 / 1024.0 / 1024.0);if (maxMemory < 2 * 1024 * 1024 * 1024L) { // 2GBSystem.out.println("  ⚠️ 建议: 生产环境堆内存至少2GB");}// 检查元空间设置List<MemoryPoolMXBean> pools = ManagementFactory.getMemoryPoolMXBeans();for (MemoryPoolMXBean pool : pools) {if ("Metaspace".equals(pool.getName())) {long metaspaceMax = pool.getUsage().getMax();System.out.printf("  - 元空间最大: %.2fMB%n", metaspaceMax / 1024.0 / 1024.0);}}}private void checkGCSettings() {List<GarbageCollectorMXBean> gcBeans = ManagementFactory.getGarbageCollectorMXBeans();System.out.println("2. GC设置检查:");for (GarbageCollectorMXBean gcBean : gcBeans) {System.out.printf("  - GC算法: %s%n", gcBean.getName());// 检查GC日志配置String gcLog = System.getProperty("Xlog:gc");if (gcLog == null) {System.out.println("  ⚠️ 建议: 启用GC日志记录");}}}private void checkJITSettings() {System.out.println("3. JIT编译器检查:");// 检查编译器配置String compiler = System.getProperty("java.compiler");if (compiler == null) {System.out.println("  - 使用默认JIT编译器");}// 检查分层编译String tieredCompilation = System.getProperty("XX:+TieredCompilation");if (tieredCompilation == null) {System.out.println("  ✅ 分层编译已启用");}}private void checkMonitoringSettings() {System.out.println("4. 监控配置检查:");// 检查JMX配置String jmxPort = System.getProperty("com.sun.management.jmxremote.port");if (jmxPort == null) {System.out.println("  ⚠️ 建议: 配置JMX远程监控");}// 检查飞行记录器String flightRecorder = System.getProperty("XX:+FlightRecorder");if (flightRecorder == null) {System.out.println("  💡 提示: 考虑启用Java飞行记录器");}}private void checkSecuritySettings() {System.out.println("5. 安全设置检查:");// 检查随机数生成器String secureRandom = System.getProperty("java.security.egd");if (secureRandom == null) {System.out.println("  ⚠️ 建议: 配置安全随机数生成器");}// 检查安全管理器SecurityManager securityManager = System.getSecurityManager();if (securityManager == null) {System.out.println("  - 未启用安全管理器");}}// 性能基准测试public void runPerformanceBenchmark() {System.out.println("=== 性能基准测试 ===");benchmarkMemoryAllocation();benchmarkGCPause();benchmarkCPUOperations();benchmarkIOOperations();}private void benchmarkMemoryAllocation() {long startTime = System.currentTimeMillis();List<byte[]> objects = new ArrayList<>();for (int i = 0; i < 100000; i++) {objects.add(new byte[1024]); // 分配1KB对象}long duration = System.currentTimeMillis() - startTime;System.out.printf("内存分配测试: 创建%d个对象, 耗时%dms%n", objects.size(), duration);}private void benchmarkGCPause() {long startTime = System.currentTimeMillis();System.gc(); // 提示GClong gcTime = System.currentTimeMillis() - startTime;System.out.printf("GC暂停时间: %dms%n", gcTime);}private void benchmarkCPUOperations() {long startTime = System.nanoTime();long result = 0;for (int i = 0; i < 1000000; i++) {result += Math.sqrt(i) * Math.log(i + 1);}long duration = System.nanoTime() - startTime;System.out.printf("CPU计算测试: 耗时%.2fms%n", duration / 1000000.0);}private void benchmarkIOOperations() {long startTime = System.currentTimeMillis();try {// 模拟文件操作Path tempFile = Files.createTempFile("benchmark", ".txt");List<String> lines = new ArrayList<>();for (int i = 0; i < 10000; i++) {lines.add("Line " + i + ": " + UUID.randomUUID());}Files.write(tempFile, lines);Files.deleteIfExists(tempFile);} catch (IOException e) {System.out.println("IO测试失败: " + e.getMessage());}long duration = System.currentTimeMillis() - startTime;System.out.printf("IO操作测试: 耗时%dms%n", duration);}
}