Java性能调优笔记
2015-12-10 10:15
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调优步骤：衡量系统现状、设定调优目标、寻找性能瓶颈、性能调优、衡量是否到达目标(如果未到达目标，需重新寻找性能瓶颈）、性能调优结束。
寻找性能瓶颈
性能瓶颈的表象：资源消耗过多、外部处理系统的性能不足、资源消耗不多但程序的响应速度却仍达不到要求。
资源消耗：CPU、文件IO、网络IO、内存。
外部处理系统的性能不足：所调用的其他系统提供的功能或数据库操作的响应速度不够。
资源消耗不多但程序的响应速度却仍达不到要求：程序代码运行效率不够高、未充分使用资源、程序结构不合理。
CPU消耗分析
CPU主要用于中断、内核、用户进程的任务处理，优先级为中断>内核>用户进程。
上下文切换：
每个线程分配一定的执行时间，当到达执行时间、线程中有IO阻塞或高优先级线程要执行时，将切换执行的线程。在切换时要存储目前线程的执行状态，并恢复要执行的线程的状态。
对于Java应用，典型的是在进行文件IO操作、网络IO操作、锁等待、线程Sleep时，当前线程会进入阻塞或休眠状态，从而触发上下文切换，上下文切换过多会造成内核占据较多的CPU的使用。
运行队列：
每个CPU核都维护一个可运行的线程队列。系统的load主要由CPU的运行队列来决定。
运行队列值越大，就意味着线程会要消耗越长的时间才能执行完成。
利用率：
CPU在用户进程、内核、中断处理、IO等待、空闲，这五个部分使用百分比。
文件IO消耗分析
Linux在操作文件时，将数据放入文件缓存区，直到内存不够或系统要释放内存给用户进程使用。所以通常情况下只有写文件和第一次读取文件时会产生真正的文件IO。
对于Java应用，造成文件IO消耗高主要是多个线程需要进行大量内容写入（例如频繁的日志写入）的动作、磁盘设备本身的处理速度慢、文件系统慢、操作的文件本身已经很大。
网络IO消耗分析
对于分布式Java应用，网卡中断是不是均衡分配到各CPU(cat/proc/interrupts查看)。
内存消耗分析（-Xms和-Xmx设为相同的值，避免运行期JVM堆内存要不断申请内存）
对于Java应用，内存的消耗主要在Java堆内存上，只有创建线程和使用Direct ByteBuffer才会操作JVM堆外的内存。
JVM内存消耗过多会导致GC执行频繁，CPU消耗增加，应用线程的执行速度严重下降，甚至造成OutOfMemoryError，最终导致Java进程退出。
JVM堆外的内存
swap的消耗、物理内存的消耗、JVM内存的消耗。
程序执行慢原因分析
锁竞争激烈：很多线程竞争互斥资源，但资源有限， 造成其他线程都处于等待状态。
未充分使用硬件资源：线程操作被串行化。
数据量增长：单表数据量太大（如1个亿）造成数据库读写速度大幅下降（操作此表）。
调优
JVM调优（最关键参数为：-Xms -Xmx -Xmn -XX:SurvivorRatio
-XX:MaxTenuringThreshold）
代大小调优：避免新生代大小设置过小、避免新生代大小设置过大、避免Survivor设置过小或过大、合理设置新生代存活周期。
-Xmn
调整新生代大小，新生代越大通常也意味着更多对象会在minor GC阶段被回收，但可能有可能造成旧生代大小，造成频繁触发Full
GC，甚至是OutOfMemoryError。
-XX:SurvivorRatio调整Eden区与Survivor区的大小，Eden
区越大通常也意味着minor GC发生频率越低，但可能有可能造成Survivor区太小，导致对象minor
GC后就直接进入旧生代，从而更频繁触发Full GC。
GC策略的调优：CMS
GC多数动作是和应用并发进行的，确实可以减小GC动作给应用造成的暂停时间。对于Web应用非常需要一个对应用造成暂停时间短的GC，再加上Web应用
的瓶颈都不在CPU上，在G1还不够成熟的情况下，CMS GC是不错的选择。
（如果系统不是CPU密集型，且从新生代进入旧生代的大部分对象是可以回收的，那么采用CMS
GC可以更好地在旧生代满之前完成对象的回收，更大程度降低Full GC发生的可能）
在调整了内存管理方面的参数后应通过-XX:PrintGCDetails、-XX:+PrintGCTimeStamps、
-XX:+PrintGCApplicationStoppedTime以及jstat或visualvm等方式观察调整后的GC状况。
出内存管理以外的其他方面的调优参数：-XX:CompileThreshold、-XX:+UseFastAccessorMethods、
-XX:+UseBaiasedLocking。
程序调优
CPU消耗严重的解决方法
CPU us高的解决方法：
CPU us 高的原因主要是执行线程不需要任何挂起动作，且一直执行，导致CPU 没有机会去调度执行其他的线程。
调优方案： 增加Thread.sleep，以释放CPU 的执行权，降低CPU 的消耗。以损失单次执行性能为代价的，但由于其降低了CPU 的消耗，对于多线程的应用而言，反而提高了总体的平均性能。
（在实际的Java应用中类似场景， 对于这种场景最佳方式是改为采用wait/notify机制）
对于其他类似循环次数过多、正则、计算等造成CPU us过高的状况， 则需要结合业务调优。
对于GC频繁，则需要通过JVM调优或程序调优，降低GC的执行次数。
CPU sy高的解决方法：
CPU sy 高的原因主要是线程的运行状态要经常切换，对于这种情况，常见的一种优化方法是减少线程数。
调优方案： 将线程数降低
这种调优过后有可能会造成CPU us过高，所以合理设置线程数非常关键。
对于Java分布式应用，还有一种典型现象是应用中有较多的网络IO操作和确实需要一些锁竞争机制（如数据库连接池），但为了能够支撑搞得并发量，可采用协程（Coroutine）来支撑更高的并发量，避免并发量上涨后造成CPU sy消耗严重、系统load迅速上涨和系统性能下降。
在Java中实现协程的框架有Kilim，Kilim执行一项任务创建Task，使用Task的暂停机制，而不是Thread，Kilim承担了线程调度以及上下切换动作，Task相对于原生Thread而言就轻量级多了，且能更好利用CPU。Kilim带来的是线程使用率的提升，但同时由于要在JVM堆中保存Task上下文信息，因此在采用Kilim的情况下要消耗更多的内存。（目前JDK 7中也有一个支持协程方式的实现，另外基于JVM的Scala的Actor也可用于在Java使用协程）
文件IO消耗严重的解决方法
从程序的角度而言，造成文件IO消耗严重的原因主要是多个线程在写进行大量的数据到同一文件，导致文件很快变得很大，从而写入速度越来越慢，并造成各线程激烈争抢文件锁。
常用调优方法：
异步写文件
批量读写
限流
限制文件大小
网络IO消耗严重的解决方法
从程序的角度而言，造成网络IO消耗严重的原因主要是同时需要发送或接收的包太多。
常用调优方法：
限流，限流通常是限制发送packet的频率，从而在网络IO消耗可接受的情况下来发送packget。
内存消耗严重的解决方法
释放不必要的引用：代码持有了不需要的对象引用，造成这些对象无法被GC，从而占据了JVM堆内存。（使用ThreadLocal：注意在线程内动作执行完毕时，需执行ThreadLocal.set把对象清除，避免持有不必要的对象引用）
使用对象缓存池：创建对象要消耗一定的CPU以及内存，使用对象缓存池一定程度上可降低JVM堆内存的使用。
采用合理的缓存失效算法：如果放入太多对象在缓存池中，反而会造成内存的严重消耗， 同时由于缓存池一直对这些对象持有引用，从而造成Full GC增多，对于这种状况要合理控制缓存池的大小，避免缓存池的对象数量无限上涨。（经典的缓存失效算法来清除缓存池中的对象：FIFO、LRU、LFU等）
合理使用SoftReference和WeekReference：SoftReference的对象会在内存不够用的时候回收，WeekReference的对象会在Full GC的时候回收。
资源消耗不多但程序执行慢的情况的解决方法
降低锁竞争： 多线多了，锁竞争的状况会比较明显，这时候线程很容易处于等待锁的状况，从而导致性能下降以及CPU sy上升。
使用并发包中的类：大多数采用了lock-free、nonblocking算法。
使用Treiber算法：基于CAS以及AtomicReference。
使用Michael-Scott非阻塞队列算法：基于CAS以及AtomicReference，典型ConcurrentLindkedQueue。
（基于CAS和AtomicReference来实现无阻塞是不错的选择，但值得注意的是，lock-free算法需不断的循环比较来保证资源的一致性的，对于冲突较多的应用场景而言，会带来更高的CPU消耗，因此不一定采用CAS实现无阻塞的就一定比采用lock方式的性能好。 还有一些无阻塞算法的改进：MCAS、WSTM等）
尽可能少用锁：尽可能只对需要控制的资源做加锁操作（通常没有必要对整个方法加锁，尽可能让锁最小化，只对互斥及原子操作的地方加锁，加锁时尽可能以保护资源的最小化粒度为单位–如只对需要保护的资源加锁而不是this）。
拆分锁：独占锁拆分为多把锁（读写锁拆分、类似ConcurrentHashMap中默认拆分为16把锁），很多程度上能提高读写的性能，但需要注意在采用拆分锁后，全局性质的操作会变得比较复杂（如ConcurrentHashMap中size操作）。（拆分锁太多也会造成副作用，如CPU消耗明显增加）
去除读写操作的互斥：在修改时加锁，并复制对象进行修改，修改完毕后切换对象的引用，从而读取时则不加锁。这种称为CopyOnWrite，CopyOnWriteArrayList是典型实现，好处是可以明显提升读的性能，适合读多写少的场景， 但由于写操作每次都要复制一份对象，会消耗更多的内存。
充分利用硬件资源（CPU和内存）：
充分利用CPU
在能并行处理的场景中未使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）， 例如单线程的计算，可以拆分为多个线程分别计算，最后将结果合并，JDK 7中的fork-join框架。
Amdahl定律公式：1/(F+(1-F)/N)。
充分利用内存
数据的缓存、耗时资源的缓存（数据库连接创建、网络连接的创建等）、页面片段的缓存。
毕竟内存的读取肯定远快于硬盘、网络的读取， 在内存消耗可接受、GC频率、以及系统结构（例如集群环境可能会带来缓存的同步）可接受情况下，应充分利用内存来缓存数据，提升系统的性能。
总结：
好的调优策略是收益比（调优后提升的效果/调优改动所需付出的代价）最高的，通常来说简单的系统调优比较好做，因此尽量保持单机上应用的纯粹性， 这是大型系统的基本架构原则。
调优的三大有效原则：充分而不过分使用硬件资源、合理调整JVM、合理使用JDK包。
学习参考资料：
《分布式Java应用：基础与实践》
补充《分布式Java应用：基础与实践》一些代码样例：
cpu———————————–
CpuNotUseEffectiveDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.cpu;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
/**
* 未充分利用CPU：在能并行处理的场景中未使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）
*
* @author yangwm Aug 25, 2010 9:54:50 AM
*/
public class CpuNotUseEffectiveDemo {
private static int executeTimes = 10;
private static int taskCount = 200;
public static void main(String[] args) throws Exception {
Task task = new Task();
for (int i = 0; i < taskCount; i++) {
task.addTask(Integer.toString(i));
}
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
Thread thread = new Thread(task);
thread.start();
thread.join();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) TaskCount Per Round( ” + taskCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class Task implements Runnable {
List<String> tasks = new ArrayList<String>();
Random random = new Random();
boolean exitFlag = false;
public void addTask(String task) {
List<String> copyTasks = new ArrayList<String>(tasks);
copyTasks.add(task);
tasks = copyTasks;
}
@Override
public void run() {
List<String> runTasks = tasks;
List<String> removeTasks = new ArrayList<String>();
for (String task : runTasks) {
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
removeTasks.add(task);
}
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) TaskCount Per Round( 200 ) Execute Time ( 10687 ) ms
*/
/**
*
*/
package tune.program.cpu;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
/**
* 未充分利用CPU：在能并行处理的场景中未使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）
*
* @author yangwm Aug 25, 2010 9:54:50 AM
*/
public class CpuNotUseEffectiveDemo {
private static int executeTimes = 10;
private static int taskCount = 200;
public static void main(String[] args) throws Exception {
Task task = new Task();
for (int i = 0; i < taskCount; i++) {
task.addTask(Integer.toString(i));
}
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
Thread thread = new Thread(task);
thread.start();
thread.join();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) TaskCount Per Round( ” + taskCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class Task implements Runnable {
List<String> tasks = new ArrayList<String>();
Random random = new Random();
boolean exitFlag = false;
public void addTask(String task) {
List<String> copyTasks = new ArrayList<String>(tasks);
copyTasks.add(task);
tasks = copyTasks;
}
@Override
public void run() {
List<String> runTasks = tasks;
List<String> removeTasks = new ArrayList<String>();
for (String task : runTasks) {
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
removeTasks.add(task);
}
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) TaskCount Per Round( 200 ) Execute Time ( 10687 ) ms
*/
CpuUseEffectiveDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.cpu;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
/**
* 充分利用CPU：在能并行处理的场景中使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）
*
* @author yangwm Aug 25, 2010 9:54:50 AM
*/
public class CpuUseEffectiveDemo {
private static int executeTimes = 10;
private static int taskCount = 200;
private static final int TASK_THREADCOUNT = 16;
private static CountDownLatch latch;
public static void main(String[] args) throws Exception {
Task[] tasks = new Task[TASK_THREADCOUNT];
for (int i = 0; i < TASK_THREADCOUNT; i++) {
tasks[i] = new Task();
}
for (int i = 0; i < taskCount; i++) {
int mod = i % TASK_THREADCOUNT;
tasks[mod].addTask(Integer.toString(i));
}
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(TASK_THREADCOUNT);
for (int j = 0; j < TASK_THREADCOUNT; j++) {
Thread thread = new Thread(tasks[j]);
thread.start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) TaskCount Per Round( ” + taskCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class Task implements Runnable {
List<String> tasks = new ArrayList<String>();
Random random = new Random();
boolean exitFlag = false;
public void addTask(String task) {
List<String> copyTasks = new ArrayList<String>(tasks);
copyTasks.add(task);
tasks = copyTasks;
}
@Override
public void run() {
List<String> runTasks = tasks;
List<String> removeTasks = new ArrayList<String>();
for (String task : runTasks) {
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
removeTasks.add(task);
}
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
latch.countDown();
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) TaskCount Per Round( 200 ) Execute Time ( 938 ) ms
*/
/**
*
*/
package tune.program.cpu;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
/**
* 充分利用CPU：在能并行处理的场景中使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）
*
* @author yangwm Aug 25, 2010 9:54:50 AM
*/
public class CpuUseEffectiveDemo {
private static int executeTimes = 10;
private static int taskCount = 200;
private static final int TASK_THREADCOUNT = 16;
private static CountDownLatch latch;
public static void main(String[] args) throws Exception {
Task[] tasks = new Task[TASK_THREADCOUNT];
for (int i = 0; i < TASK_THREADCOUNT; i++) {
tasks[i] = new Task();
}
for (int i = 0; i < taskCount; i++) {
int mod = i % TASK_THREADCOUNT;
tasks[mod].addTask(Integer.toString(i));
}
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(TASK_THREADCOUNT);
for (int j = 0; j < TASK_THREADCOUNT; j++) {
Thread thread = new Thread(tasks[j]);
thread.start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) TaskCount Per Round( ” + taskCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class Task implements Runnable {
List<String> tasks = new ArrayList<String>();
Random random = new Random();
boolean exitFlag = false;
public void addTask(String task) {
List<String> copyTasks = new ArrayList<String>(tasks);
copyTasks.add(task);
tasks = copyTasks;
}
@Override
public void run() {
List<String> runTasks = tasks;
List<String> removeTasks = new ArrayList<String>();
for (String task : runTasks) {
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
removeTasks.add(task);
}
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
latch.countDown();
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) TaskCount Per Round( 200 ) Execute Time ( 938 ) ms
*/
fileio——————————————————————-
IOWaitHighDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.fileio;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.util.Random;
/**
* 文件IO消耗严重的原因主要是多个线程在写进行大量的数据到同一文件，
* 导致文件很快变得很大，从而写入速度越来越慢，并造成各线程激烈争抢文件锁。
*
* @author yangwm Aug 21, 2010 9:48:34 PM
*/
public class IOWaitHighDemo {
private String fileName = “iowait.log”;
private static int threadCount = Runtime.getRuntime().availableProcessors();
private Random random = new Random();
public static void main(String[] args) throws Exception {
if (args.length == 1) {
threadCount = Integer.parseInt(args[1]);
}
IOWaitHighDemo demo = new IOWaitHighDemo();
demo.runTest();
}
private void runTest() throws Exception {
File file = new File(fileName);
file.createNewFile();
for (int i = 0; i < threadCount; i++) {
new Thread(new Task()).start();
}
}
class Task implements Runnable {
@Override
public void run() {
while (true) {
try {
StringBuilder strBuilder = new StringBuilder(“====begin====/n”);
String threadName = Thread.currentThread().getName();
for (int i = 0; i < 100000; i++) {
strBuilder.append(threadName);
strBuilder.append(”/n”);
}
strBuilder.append(”====end====/n”);
BufferedWriter writer = new BufferedWriter(new FileWriter(fileName, true));
writer.write(strBuilder.toString());
writer.close();
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
}
}
}
}
}
/*
C:/Documents and Settings/yangwm>jstack 2656
2010-08-21 23:24:17
Full thread dump Java HotSpot(TM) Client VM (17.0-b05 mixed mode):
”DestroyJavaVM” prio=6 tid=0x00868c00 nid=0xde0 waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
”Thread-1” prio=6 tid=0x0ab9dc00 nid=0xb7c runnable [0x0b0bf000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.close0(Native Method)
at java.io.FileOutputStream.close(FileOutputStream.java:336)
at sun.nio.cs.StreamEncoder.implClose(StreamEncoder.java:320)
at sun.nio.cs.StreamEncoder.close(StreamEncoder.java:149)
- locked <0x034dd268> (a java.io.FileWriter)
at java.io.OutputStreamWriter.close(OutputStreamWriter.java:233)
at java.io.BufferedWriter.close(BufferedWriter.java:265)
- locked <0x034dd268> (a java.io.FileWriter)
at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:58)</span> </span></li><li class=""><span><span class="comment"> at java.lang.Thread.run(Thread.java:717)</span> </span></li><li class="alt"><span><span class="comment">"Thread-0" prio=6 tid=0x0ab9d400 nid=0x80c runnable [0x0b06f000]</span> </span></li><li class=""><span><span class="comment"> java.lang.Thread.State: RUNNABLE</span> </span></li><li class="alt"><span><span class="comment"> at java.io.FileOutputStream.writeBytes(Native Method)</span> </span></li><li class=""><span><span class="comment"> at java.io.FileOutputStream.write(FileOutputStream.java:292)</span> </span></li><li class="alt"><span><span class="comment"> at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)</span> </span></li><li class=""><span><span class="comment"> at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:282)</span> </span></li><li class="alt"><span><span class="comment"> at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)</span> </span></li><li class=""><span><span class="comment"> - locked <0x034e1290> (a java.io.FileWriter)</span> </span></li><li class="alt"><span><span class="comment"> at java.io.OutputStreamWriter.write(OutputStreamWriter.java:207)</span> </span></li><li class=""><span><span class="comment"> at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:128)</span> </span></li><li class="alt"><span><span class="comment"> - locked <0x034e1290> (a java.io.FileWriter)</span> </span></li><li class=""><span><span class="comment"> at java.io.BufferedWriter.write(BufferedWriter.java:229)</span> </span></li><li class="alt"><span><span class="comment"> - locked <0x034e1290> (a java.io.FileWriter)</span> </span></li><li class=""><span><span class="comment"> at java.io.Writer.write(Writer.java:157)</span> </span></li><li class="alt"><span><span class="comment"> at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:58)
at java.lang.Thread.run(Thread.java:717)
"Thread-0" prio=6 tid=0x0ab9d400 nid=0x80c runnable [0x0b06f000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:292)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:282)
at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.OutputStreamWriter.write(OutputStreamWriter.java:207)
at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:128)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.BufferedWriter.write(BufferedWriter.java:229)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.Writer.write(Writer.java:157)
at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:57)
at java.lang.Thread.run(Thread.java:717)
”Low Memory Detector” daemon prio=6 tid=0x0ab6f800 nid=0xfb0 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
”CompilerThread0” daemon prio=10 tid=0x0ab6c800 nid=0x5fc waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
”Attach Listener” daemon prio=10 tid=0x0ab67800 nid=0x6fc waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
”Signal Dispatcher” daemon prio=10 tid=0x0ab66800 nid=0x5a0 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
”Finalizer” daemon prio=8 tid=0x0ab54000 nid=0xe74 in Object.wait() [0x0ac8f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)</span> </span></li><li class="alt"><span><span class="comment"> at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)</span> </span></li><li class=""><span><span class="comment"> - locked <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
- locked <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at java.lang.ref.FinalizerFinalizerThread.run(Finalizer.java:177)</span> </span></li><li class="alt"><span><span class="comment">"Reference Handler" daemon prio=10 tid=0x0ab4f800 nid=0x8a4 in Object.wait() [0x0ac3f000]</span> </span></li><li class=""><span><span class="comment"> java.lang.Thread.State: WAITING (on object monitor)</span> </span></li><li class="alt"><span><span class="comment"> at java.lang.Object.wait(Native Method)</span> </span></li><li class=""><span><span class="comment"> - waiting on <0x02f15af8> (a java.lang.ref.ReferenceFinalizerThread.run(Finalizer.java:177)
"Reference Handler" daemon prio=10 tid=0x0ab4f800 nid=0x8a4 in Object.wait() [0x0ac3f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x02f15af8> (a java.lang.ref.ReferenceLock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.ReferenceReferenceHandler.run(Reference.java:133)</span> </span></li><li class="alt"><span><span class="comment"> - locked <0x02f15af8> (a java.lang.ref.ReferenceReferenceHandler.run(Reference.java:133)
- locked <0x02f15af8> (a java.lang.ref.ReferenceLock)
”VM Thread” prio=10 tid=0x0ab4a800 nid=0x1d0 runnable
”VM Periodic Task Thread” prio=10 tid=0x0ab7d400 nid=0x464 waiting on condition
JNI global references: 693
C:/Documents and Settings/yangwm>
*/
/**
*
*/
package tune.program.fileio;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.util.Random;
/**
* 文件IO消耗严重的原因主要是多个线程在写进行大量的数据到同一文件，
* 导致文件很快变得很大，从而写入速度越来越慢，并造成各线程激烈争抢文件锁。
*
* @author yangwm Aug 21, 2010 9:48:34 PM
*/
public class IOWaitHighDemo {
private String fileName = “iowait.log”;
private static int threadCount = Runtime.getRuntime().availableProcessors();
private Random random = new Random();
public static void main(String[] args) throws Exception {
if (args.length == 1) {
threadCount = Integer.parseInt(args[1]);
}
IOWaitHighDemo demo = new IOWaitHighDemo();
demo.runTest();
}
private void runTest() throws Exception {
File file = new File(fileName);
file.createNewFile();
for (int i = 0; i < threadCount; i++) {
new Thread(new Task()).start();
}
}
class Task implements Runnable {
@Override
public void run() {
while (true) {
try {
StringBuilder strBuilder = new StringBuilder(“====begin====/n”);
String threadName = Thread.currentThread().getName();
for (int i = 0; i < 100000; i++) {
strBuilder.append(threadName);
strBuilder.append(“/n”);
}
strBuilder.append(“====end====/n”);
BufferedWriter writer = new BufferedWriter(new FileWriter(fileName, true));
writer.write(strBuilder.toString());
writer.close();
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
}
}
}
}
}
/*
C:/Documents and Settings/yangwm>jstack 2656
2010-08-21 23:24:17
Full thread dump Java HotSpot(TM) Client VM (17.0-b05 mixed mode):
“DestroyJavaVM” prio=6 tid=0x00868c00 nid=0xde0 waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
“Thread-1” prio=6 tid=0x0ab9dc00 nid=0xb7c runnable [0x0b0bf000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.close0(Native Method)
at java.io.FileOutputStream.close(FileOutputStream.java:336)
at sun.nio.cs.StreamEncoder.implClose(StreamEncoder.java:320)
at sun.nio.cs.StreamEncoder.close(StreamEncoder.java:149)
- locked <0x034dd268> (a java.io.FileWriter)
at java.io.OutputStreamWriter.close(OutputStreamWriter.java:233)
at java.io.BufferedWriter.close(BufferedWriter.java:265)
- locked <0x034dd268> (a java.io.FileWriter)
at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:58)atjava.lang.Thread.run(Thread.java:717)“Thread−0”prio=6tid=0x0ab9d400nid=0x80crunnable[0x0b06f000]java.lang.Thread.State:RUNNABLEatjava.io.FileOutputStream.writeBytes(NativeMethod)atjava.io.FileOutputStream.write(FileOutputStream.java:292)atsun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)atsun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:282)atsun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)−locked<0x034e1290>(ajava.io.FileWriter)atjava.io.OutputStreamWriter.write(OutputStreamWriter.java:207)atjava.io.BufferedWriter.flushBuffer(BufferedWriter.java:128)−locked<0x034e1290>(ajava.io.FileWriter)atjava.io.BufferedWriter.write(BufferedWriter.java:229)−locked<0x034e1290>(ajava.io.FileWriter)atjava.io.Writer.write(Writer.java:157)attune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:58)
at java.lang.Thread.run(Thread.java:717)
“Thread-0” prio=6 tid=0x0ab9d400 nid=0x80c runnable [0x0b06f000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:292)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:282)
at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.OutputStreamWriter.write(OutputStreamWriter.java:207)
at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:128)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.BufferedWriter.write(BufferedWriter.java:229)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.Writer.write(Writer.java:157)
at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:57)
at java.lang.Thread.run(Thread.java:717)
“Low Memory Detector” daemon prio=6 tid=0x0ab6f800 nid=0xfb0 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
“CompilerThread0” daemon prio=10 tid=0x0ab6c800 nid=0x5fc waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
“Attach Listener” daemon prio=10 tid=0x0ab67800 nid=0x6fc waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
“Signal Dispatcher” daemon prio=10 tid=0x0ab66800 nid=0x5a0 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
“Finalizer” daemon prio=8 tid=0x0ab54000 nid=0xe74 in Object.wait() [0x0ac8f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)atjava.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)−locked<0x02f15d90>(ajava.lang.ref.ReferenceQueueLock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
- locked <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at java.lang.ref.FinalizerFinalizerThread.run(Finalizer.java:177)“ReferenceHandler”daemonprio=10tid=0x0ab4f800nid=0x8a4inObject.wait()[0x0ac3f000]java.lang.Thread.State:WAITING(onobjectmonitor)atjava.lang.Object.wait(NativeMethod)−waitingon<0x02f15af8>(ajava.lang.ref.ReferenceFinalizerThread.run(Finalizer.java:177)
“Reference Handler” daemon prio=10 tid=0x0ab4f800 nid=0x8a4 in Object.wait() [0x0ac3f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x02f15af8> (a java.lang.ref.ReferenceLock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.ReferenceReferenceHandler.run(Reference.java:133)−locked<0x02f15af8>(ajava.lang.ref.ReferenceReferenceHandler.run(Reference.java:133)
- locked <0x02f15af8> (a java.lang.ref.ReferenceLock)
“VM Thread” prio=10 tid=0x0ab4a800 nid=0x1d0 runnable
“VM Periodic Task Thread” prio=10 tid=0x0ab7d400 nid=0x464 waiting on condition
JNI global references: 693
C:/Documents and Settings/yangwm>
*/
LogControl
[java] view plaincopyprint?/**
*
*/
package tune.program.fileio;
import java.util.concurrent.atomic.AtomicInteger;
/**
* 日志控制：采用简单策略为统计一段时间内日志输出频率， 当超出这个频率时，一段时间内不再写log
*
* @author yangwm Aug 24, 2010 10:41:43 AM
*/
public class LogControl {
public static void main(String[] args) {
for (int i = 1; i <= 1000; i++) {
if (LogControl.isLog()) {
//logger.error(errorInfo, throwable);
System.out.println(”errorInfo ” + i);
}
//
if (i % 100 == 0) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
private static final long INTERVAL = 1000;
private static final long PUNISH_TIME = 5000;
private static final int ERROR_THRESHOLD = 100;
private static AtomicInteger count = new AtomicInteger(0);
private static long beginTime;
private static long punishTimeEnd;
// 由于控制不用非常精确， 因此忽略此处的并发问题
public static boolean isLog() {
//System.out.println(count.get() + ”, ” + beginTime + ”, ” + punishTimeEnd + ”, ” + System.currentTimeMillis());
// 不写日志阶段
if (punishTimeEnd > 0 && punishTimeEnd > System.currentTimeMillis()) {
return false;
}
// 重新计数
if (count.getAndIncrement() == 0) {
beginTime = System.currentTimeMillis();
return true;
} else { // 已在计数
// 超过阀门值， 设置count为0并设置一段时间内不写日志
if (count.get() > ERROR_THRESHOLD) {
count.set(0);
punishTimeEnd = PUNISH_TIME + System.currentTimeMillis();
return false;
}
// 没超过阀门值， 且当前时间已超过计数周期，则重新计算
else if (System.currentTimeMillis() > (beginTime + INTERVAL)) {
count.set(0);
}
return true;
}
}
}
/*
errorInfo 1
errorInfo 2
……
errorInfo 99
errorInfo 100
errorInfo 601
errorInfo 602
……
errorInfo 699
errorInfo 700
*/
/**
*
*/
package tune.program.fileio;
import java.util.concurrent.atomic.AtomicInteger;
/**
* 日志控制：采用简单策略为统计一段时间内日志输出频率， 当超出这个频率时，一段时间内不再写log
*
* @author yangwm Aug 24, 2010 10:41:43 AM
*/
public class LogControl {
public static void main(String[] args) {
for (int i = 1; i <= 1000; i++) {
if (LogControl.isLog()) {
//logger.error(errorInfo, throwable);
System.out.println(“errorInfo ” + i);
}
//
if (i % 100 == 0) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
private static final long INTERVAL = 1000;
private static final long PUNISH_TIME = 5000;
private static final int ERROR_THRESHOLD = 100;
private static AtomicInteger count = new AtomicInteger(0);
private static long beginTime;
private static long punishTimeEnd;
// 由于控制不用非常精确， 因此忽略此处的并发问题
public static boolean isLog() {
//System.out.println(count.get() + “, ” + beginTime + “, ” + punishTimeEnd + “, ” + System.currentTimeMillis());
// 不写日志阶段
if (punishTimeEnd > 0 && punishTimeEnd > System.currentTimeMillis()) {
return false;
}
// 重新计数
if (count.getAndIncrement() == 0) {
beginTime = System.currentTimeMillis();
return true;
} else { // 已在计数
// 超过阀门值， 设置count为0并设置一段时间内不写日志
if (count.get() > ERROR_THRESHOLD) {
count.set(0);
punishTimeEnd = PUNISH_TIME + System.currentTimeMillis();
return false;
}
// 没超过阀门值， 且当前时间已超过计数周期，则重新计算
else if (System.currentTimeMillis() > (beginTime + INTERVAL)) {
count.set(0);
}
return true;
}
}
}
/*
errorInfo 1
errorInfo 2
……
errorInfo 99
errorInfo 100
errorInfo 601
errorInfo 602
……
errorInfo 699
errorInfo 700
*/
memory——————————————————————-
MemoryHighDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.memory;
import java.nio.ByteBuffer;
/**
* direct bytebuffer消耗的是jvm堆外的内存，但同样是基于GC方式来释放的。
*
* @author yangwm Aug 21, 2010 9:40:18 PM
*/
public class MemoryHighDemo {
public static void main(String[] args) throws Exception{
Thread.sleep(20000);
System.out.println(”read to create bytes,so jvm heap will be used”);
byte[] bytes=new byte[128*1000*1000];
bytes[0]=1;
bytes[1]=2;
Thread.sleep(10000);
System.out.println(”read to allocate & put direct bytebuffer,no jvm heap should be used”);
ByteBuffer buffer=ByteBuffer.allocateDirect(128*1024*1024);
buffer.put(bytes);
buffer.flip();
Thread.sleep(10000);
System.out.println(”ready to gc,jvm heap will be freed”);
bytes=null;
System.gc();
Thread.sleep(10000);
System.out.println(”read to get bytes,then jvm heap will be used”);
byte[] resultbytes=new byte[128*1000*1000];
buffer.get(resultbytes);
System.out.println(”resultbytes[1] is: ”+resultbytes[1]);
Thread.sleep(10000);
System.out.println(”read to gc all”);
buffer=null;
resultbytes=null;
System.gc();
Thread.sleep(10000);
}
}
/*
D:/study/tempProject/JavaLearn/classes>java -Xms140M -Xmx140M tune.MemoryHighDemo
read to create bytes,so jvm heap will be used
read to allocate & put direct bytebuffer,no jvm heap should be used
ready to gc,jvm heap will be freed
read to get bytes,then jvm heap will be used
resultbytes[1] is: 2
read to gc all
*/
/**
*
*/
package tune.program.memory;
import java.nio.ByteBuffer;
/**
* direct bytebuffer消耗的是jvm堆外的内存，但同样是基于GC方式来释放的。
*
* @author yangwm Aug 21, 2010 9:40:18 PM
*/
public class MemoryHighDemo {
public static void main(String[] args) throws Exception{
Thread.sleep(20000);
System.out.println(“read to create bytes,so jvm heap will be used”);
byte[] bytes=new byte[128*1000*1000];
bytes[0]=1;
bytes[1]=2;
Thread.sleep(10000);
System.out.println(“read to allocate & put direct bytebuffer,no jvm heap should be used”);
ByteBuffer buffer=ByteBuffer.allocateDirect(128*1024*1024);
buffer.put(bytes);
buffer.flip();
Thread.sleep(10000);
System.out.println(“ready to gc,jvm heap will be freed”);
bytes=null;
System.gc();
Thread.sleep(10000);
System.out.println(“read to get bytes,then jvm heap will be used”);
byte[] resultbytes=new byte[128*1000*1000];
buffer.get(resultbytes);
System.out.println(“resultbytes[1] is: “+resultbytes[1]);
Thread.sleep(10000);
System.out.println(“read to gc all”);
buffer=null;
resultbytes=null;
System.gc();
Thread.sleep(10000);
}
}
/*
D:/study/tempProject/JavaLearn/classes>java -Xms140M -Xmx140M tune.MemoryHighDemo
read to create bytes,so jvm heap will be used
read to allocate & put direct bytebuffer,no jvm heap should be used
ready to gc,jvm heap will be freed
read to get bytes,then jvm heap will be used
resultbytes[1] is: 2
read to gc all
*/
ObjectCachePool
[java] view plaincopyprint?/**
*
*/
package tune.program.memory;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
/**
* 采用合理的缓存失效算法: FIFO、LRU、LFU等
*
* @author yangwm Aug 24, 2010 6:06:48 PM
*/
public class ObjectCachePool<K, V> {
public static void main(String[] args) {
// FIFO_POLICY
int size = 10;
int policy = 1;
ObjectCachePool<Integer, Integer> objectCachePool = new ObjectCachePool<Integer, Integer>(size, policy);
for (int i = 1; i <= 15; i++) {
objectCachePool.put(i, i);
}
for (int i = 15; i >= 1; i–) {
objectCachePool.put(i, i);
}
System.out.println(”size(“ + size + “), policy(“ + policy + “) FIFO ”);
for (Map.Entry<Integer, Integer> entry : objectCachePool.entrySet()) {
System.out.println(entry.getKey() + ”, ” + entry.getValue());
}
// LRU_POLICY
size = 10;
policy = 2;
objectCachePool = new ObjectCachePool<Integer, Integer>(size, policy);
for (int i = 1; i <= 15; i++) {
objectCachePool.put(i, i);
}
for (int i = 15; i >= 1; i–) {
objectCachePool.put(i, i);
}
System.out.println(”size(“ + size + “), policy(“ + policy + “) LRU ”);
for (Map.Entry<Integer, Integer> entry : objectCachePool.entrySet()) {
System.out.println(entry.getKey() + ”, ” + entry.getValue());
}
}
private static final int FIFO_POLICY = 1;
private static final int LRU_POLICY = 2;
private static final int DEFAULT_SIZE = 10;
private Map<K, V> cacheObjects;
public ObjectCachePool() {
this(DEFAULT_SIZE);
}
public ObjectCachePool(int size) {
this(size, FIFO_POLICY);
}
public ObjectCachePool(final int size, final int policy) {
switch (policy) {
case FIFO_POLICY:
cacheObjects = new LinkedHashMap<K, V>(size) {
/**
*
*/
private static final long serialVersionUID = 1L;
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > size;
}
};
break;
case LRU_POLICY:
cacheObjects = new LinkedHashMap<K, V>(size, 0.75f, true) {
/**
*
*/
private static final long serialVersionUID = 1L;
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > size;
}
};
break;
default:
throw new IllegalArgumentException(“Unknown policy: ” + policy);
}
}
public void put(K key, V value) {
cacheObjects.put(key, value);
}
public void get(K key) {
cacheObjects.get(key);
}
public void remove(K key) {
cacheObjects.remove(key);
}
public void clear() {
cacheObjects.clear();
}
public Set<Map.Entry<K, V>> entrySet() {
return cacheObjects.entrySet();
}
}
/*
size(10), policy(1) FIFO
11, 11
12, 12
13, 13
14, 14
15, 15
5, 5
4, 4
3, 3
2, 2
1, 1
size(10), policy(2) LRU
10, 10
9, 9
8, 8
7, 7
6, 6
5, 5
4, 4
3, 3
2, 2
1, 1
*/
/**
*
*/
package tune.program.memory;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
/**
* 采用合理的缓存失效算法: FIFO、LRU、LFU等
*
* @author yangwm Aug 24, 2010 6:06:48 PM
*/
public class ObjectCachePool<K, V> {
public static void main(String[] args) {
// FIFO_POLICY
int size = 10;
int policy = 1;
ObjectCachePool<Integer, Integer> objectCachePool = new ObjectCachePool<Integer, Integer>(size, policy);
for (int i = 1; i <= 15; i++) {
objectCachePool.put(i, i);
}
for (int i = 15; i >= 1; i–) {
objectCachePool.put(i, i);
}
System.out.println(“size(” + size + “), policy(” + policy + “) FIFO “);
for (Map.Entry<Integer, Integer> entry : objectCachePool.entrySet()) {
System.out.println(entry.getKey() + “, ” + entry.getValue());
}
// LRU_POLICY
size = 10;
policy = 2;
objectCachePool = new ObjectCachePool<Integer, Integer>(size, policy);
for (int i = 1; i <= 15; i++) {
objectCachePool.put(i, i);
}
for (int i = 15; i >= 1; i–) {
objectCachePool.put(i, i);
}
System.out.println(“size(” + size + “), policy(” + policy + “) LRU “);
for (Map.Entry<Integer, Integer> entry : objectCachePool.entrySet()) {
System.out.println(entry.getKey() + “, ” + entry.getValue());
}
}
private static final int FIFO_POLICY = 1;
private static final int LRU_POLICY = 2;
private static final int DEFAULT_SIZE = 10;
private Map<K, V> cacheObjects;
public ObjectCachePool() {
this(DEFAULT_SIZE);
}
public ObjectCachePool(int size) {
this(size, FIFO_POLICY);
}
public ObjectCachePool(final int size, final int policy) {
switch (policy) {
case FIFO_POLICY:
cacheObjects = new LinkedHashMap<K, V>(size) {
/**
*
*/
private static final long serialVersionUID = 1L;
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > size;
}
};
break;
case LRU_POLICY:
cacheObjects = new LinkedHashMap<K, V>(size, 0.75f, true) {
/**
*
*/
private static final long serialVersionUID = 1L;
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > size;
}
};
break;
default:
throw new IllegalArgumentException(“Unknown policy: ” + policy);
}
}
public void put(K key, V value) {
cacheObjects.put(key, value);
}
public void get(K key) {
cacheObjects.get(key);
}
public void remove(K key) {
cacheObjects.remove(key);
}
public void clear() {
cacheObjects.clear();
}
public Set<Map.Entry<K, V>> entrySet() {
return cacheObjects.entrySet();
}
}
/*
size(10), policy(1) FIFO
11, 11
12, 12
13, 13
14, 14
15, 15
5, 5
4, 4
3, 3
2, 2
1, 1
size(10), policy(2) LRU
10, 10
9, 9
8, 8
7, 7
6, 6
5, 5
4, 4
3, 3
2, 2
1, 1
*/
ObjectPoolDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.memory;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
/**
* 使用对象缓存池：创建对象要消耗一定的CPU以及内存，使用对象缓存池一定程度上可降低JVM堆内存的使用。
*
* @author yangwm Aug 24, 2010 4:34:47 PM
*/
public class ObjectPoolDemo {
private static int executeTimes = 10;
private static int maxFactor = 10;
private static int threadCount = 100;
private static final int NOTUSE_OBJECTPOOL = 1;
private static final int USE_OBJECTPOOL = 2;
private static int runMode = NOTUSE_OBJECTPOOL;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
Task task = new Task();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) Thread Per Round( ” + threadCount
+ ” ) Object Factor ( ” + maxFactor + “ ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class Task implements Runnable {
@Override
public void run() {
for (int j = 0; j < maxFactor; j++) {
if (runMode == USE_OBJECTPOOL) {
BigObjectPool.getInstance().getBigObject(j);
} else {
new BigObject(j);
}
}
latch.countDown();
}
}
static class BigObjectPool {
private static final BigObjectPool self = new BigObjectPool();
private final Map<Integer, BigObject> cacheObjects = new HashMap<Integer, BigObject>();
private BigObjectPool() {
}
public static BigObjectPool getInstance() {
return self;
}
public BigObject getBigObject(int factor) {
if (cacheObjects.containsKey(factor)) {
return cacheObjects.get(factor);
} else {
BigObject object = new BigObject(factor);
cacheObjects.put(factor, object);
return object;
}
}
}
static class BigObject {
private byte[] bytes = null;
public BigObject(int factor) {
bytes = new byte[(factor + 1) * 1024 * 1024];
}
public byte[] getBytes() {
return bytes;
}
}
}
/*
-Xms128M -Xmx128M -Xmn64M , runMode is NOTUSE_OBJECTPOOL:
Round: 1
……
Execute summary: Round( 10 ) Thread Per Round( 100 ) Object Factor ( 10 ) Execute Time ( 50672 ) ms
-Xms128M -Xmx128M -Xmn64M , runMode is USE_OBJECTPOOL:
Round: 1
……
Execute summary: Round( 10 ) Thread Per Round( 100 ) Object Factor ( 10 ) Execute Time ( 344 ) ms
*/
/**
*
*/
package tune.program.memory;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
/**
* 使用对象缓存池：创建对象要消耗一定的CPU以及内存，使用对象缓存池一定程度上可降低JVM堆内存的使用。
*
* @author yangwm Aug 24, 2010 4:34:47 PM
*/
public class ObjectPoolDemo {
private static int executeTimes = 10;
private static int maxFactor = 10;
private static int threadCount = 100;
private static final int NOTUSE_OBJECTPOOL = 1;
private static final int USE_OBJECTPOOL = 2;
private static int runMode = NOTUSE_OBJECTPOOL;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
Task task = new Task();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) Thread Per Round( ” + threadCount
+ ” ) Object Factor ( ” + maxFactor + ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class Task implements Runnable {
@Override
public void run() {
for (int j = 0; j < maxFactor; j++) {
if (runMode == USE_OBJECTPOOL) {
BigObjectPool.getInstance().getBigObject(j);
} else {
new BigObject(j);
}
}
latch.countDown();
}
}
static class BigObjectPool {
private static final BigObjectPool self = new BigObjectPool();
private final Map<Integer, BigObject> cacheObjects = new HashMap<Integer, BigObject>();
private BigObjectPool() {
}
public static BigObjectPool getInstance() {
return self;
}
public BigObject getBigObject(int factor) {
if (cacheObjects.containsKey(factor)) {
return cacheObjects.get(factor);
} else {
BigObject object = new BigObject(factor);
cacheObjects.put(factor, object);
return object;
}
}
}
static class BigObject {
private byte[] bytes = null;
public BigObject(int factor) {
bytes = new byte[(factor + 1) * 1024 * 1024];
}
public byte[] getBytes() {
return bytes;
}
}
}
/*
-Xms128M -Xmx128M -Xmn64M , runMode is NOTUSE_OBJECTPOOL:
Round: 1
……
Execute summary: Round( 10 ) Thread Per Round( 100 ) Object Factor ( 10 ) Execute Time ( 50672 ) ms
-Xms128M -Xmx128M -Xmn64M , runMode is USE_OBJECTPOOL:
Round: 1
……
Execute summary: Round( 10 ) Thread Per Round( 100 ) Object Factor ( 10 ) Execute Time ( 344 ) ms
*/
ThreadLocalDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.memory;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* 释放不必要的引用：代码持有了不需要的对象引用，造成这些对象无法被GC，从而占据了JVM堆内存。
* （使用ThreadLocal：注意在线程内动作执行完毕时，需执行 ThreadLocal.set把对象清除，避免持有不必要的对象引用）
*
* @author yangwm Aug 24, 2010 11:29:59 AM
*/
public class ThreadLocalDemo {
public static void main(String[] args) {
ThreadLocalDemo demo = new ThreadLocalDemo();
demo.run();
}
public void run() {
ExecutorService executor = Executors.newFixedThreadPool(1);
executor.execute(new Task());
System.gc();
}
class Task implements Runnable {
@Override
public void run() {
ThreadLocal<byte[]> localString = new ThreadLocal<byte[]>();
localString.set(new byte[1024 * 1024 * 30]);
// 业务逻辑
//localString.set(null); // 释放不必要的引用
}
}
}
/**
*
*/
package tune.program.memory;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* 释放不必要的引用：代码持有了不需要的对象引用，造成这些对象无法被GC，从而占据了JVM堆内存。
* （使用ThreadLocal：注意在线程内动作执行完毕时，需执行 ThreadLocal.set把对象清除，避免持有不必要的对象引用）
*
* @author yangwm Aug 24, 2010 11:29:59 AM
*/
public class ThreadLocalDemo {
public static void main(String[] args) {
ThreadLocalDemo demo = new ThreadLocalDemo();
demo.run();
}
public void run() {
ExecutorService executor = Executors.newFixedThreadPool(1);
executor.execute(new Task());
System.gc();
}
class Task implements Runnable {
@Override
public void run() {
ThreadLocal<byte[]> localString = new ThreadLocal<byte[]>();
localString.set(new byte[1024 * 1024 * 30]);
// 业务逻辑
//localString.set(null); // 释放不必要的引用
}
}
}
concurrent———————————————————————–
LockHotDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 锁竞争的状况会比较明显，这时候线程很容易处于等待锁的状况，从而导致性能下降以及CPU sy上升
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class LockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private final Lock lock = new ReentrantLock();
private Handler() {
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
try {
lock.lock();
// execute sth
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
lock.unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 10625 ) ms
*/
/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 锁竞争的状况会比较明显，这时候线程很容易处于等待锁的状况，从而导致性能下降以及CPU sy上升
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class LockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private final Lock lock = new ReentrantLock();
private Handler() {
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
try {
lock.lock();
// execute sth
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
lock.unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 10625 ) ms
*/
ReduceLockHotDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 尽可能少用锁：尽可能只对需要控制的资源做加锁操作
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class ReduceLockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private final Lock lock = new ReentrantLock();
private Handler() {
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
// execute sth don’t need lock
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
try {
lock.lock();
// execute sth
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
lock.unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 5547 ) ms
*/
/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 尽可能少用锁：尽可能只对需要控制的资源做加锁操作
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class ReduceLockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private final Lock lock = new ReentrantLock();
private Handler() {
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
// execute sth don’t need lock
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
try {
lock.lock();
// execute sth
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
lock.unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 5547 ) ms
*/
SplitReduceLockHotDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 尽可能少用锁：尽可能只对需要控制的资源做加锁操作
* 拆分锁：独占锁拆分为多把锁（读写锁拆分、类似ConcurrentHashMap中默认拆分为16把锁）
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class SplitReduceLockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private int lockCount = 10;
private Lock[] locks = new Lock[lockCount];
private Handler() {
for (int i = 0; i < lockCount; i++) {
locks[i] = new ReentrantLock();
}
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
// execute sth don’t need lock
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
int mod = id % lockCount;
try {
locks[mod].lock();
// execute sth
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
locks[mod].unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 843 ) ms
*/
/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 尽可能少用锁：尽可能只对需要控制的资源做加锁操作
* 拆分锁：独占锁拆分为多把锁（读写锁拆分、类似ConcurrentHashMap中默认拆分为16把锁）
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class SplitReduceLockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private int lockCount = 10;
private Lock[] locks = new Lock[lockCount];
private Handler() {
for (int i = 0; i < lockCount; i++) {
locks[i] = new ReentrantLock();
}
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
// execute sth don’t need lock
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
int mod = id % lockCount;
try {
locks[mod].lock();
// execute sth
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
locks[mod].unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 843 ) ms
*/
ConcurrentStack和StackBenchmark
[java] view plaincopyprint?/**
*
*/
package tune.program.concurrent;
import java.util.concurrent.atomic.AtomicReference;
/**
* 使用Treiber算法实现Stack：基于CAS以及AtomicReference。
*
* @author yangwm Aug 25, 2010 10:50:17 AM
*/
public class ConcurrentStack<E> {
AtomicReference<Node<E>> head = new AtomicReference<Node<E>>();
public void push(E item) {
Node<E> newHead = new Node<E>(item);
Node<E> oldHead;
do {
oldHead = head.get();
newHead.next = oldHead;
} while (!head.compareAndSet(oldHead, newHead));
}
public E pop() {
Node<E> oldHead;
Node<E> newHead;
do {
oldHead = head.get();
if (oldHead == null) {
return null;
}
newHead = oldHead.next;
} while (!head.compareAndSet(oldHead, newHead));
return oldHead.item;
}
static class Node<E> {
final E item;
Node<E> next;
public Node(E item) {
this.item = item;
}
}
}
/**
*
*/
package tune.program.concurrent;
import java.util.Stack;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
/**
* 基准测试：Treiber算法实现Stack、同步实现的Stack
*
* @author yangwm Aug 25, 2010 11:36:14 AM
*/
public class StackBenchmark {
public static void main(String[] args) throws Exception {
StackBenchmark stackBenchmark = new StackBenchmark();
stackBenchmark.run();
}
private Stack<String> stack = new Stack<String>();
private ConcurrentStack<String> concurrentStack = new ConcurrentStack<String>();
private static final int THREAD_COUNT = 300;
private CountDownLatch latch = new CountDownLatch(THREAD_COUNT);
private CyclicBarrier barrier = new CyclicBarrier(THREAD_COUNT);
public void run() throws Exception {
StackTask stackTask = new StackTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(stackTask).start();
}
latch.await();
long endTime = System.currentTimeMillis();
System.out.println(”Stack consume Time: ” + (endTime - beginTime) + “ ms”);
latch = new CountDownLatch(THREAD_COUNT);
barrier = new CyclicBarrier(THREAD_COUNT);
ConcurrentStackTask concurrentStackTask = new ConcurrentStackTask();
beginTime = System.currentTimeMillis();
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(concurrentStackTask).start();
}
latch.await();
endTime = System.currentTimeMillis();
System.out.println(”ConcurrentStack consume Time: ” + (endTime - beginTime) + “ ms”);
}
class StackTask implements Runnable {
@Override
public void run() {
try {
barrier.await();
} catch (Exception e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
stack.push(Thread.currentThread().getName());
stack.pop();
}
latch.countDown();
}
}
class ConcurrentStackTask implements Runnable {
@Override
public void run() {
try {
barrier.await();
} catch (Exception e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
concurrentStack.push(Thread.currentThread().getName());
concurrentStack.pop();
}
latch.countDown();
}
}
}
/*
Stack consume Time: 94 ms
ConcurrentStack consume Time: 63 ms
Stack consume Time: 78 ms
ConcurrentStack consume Time: 62 ms
*/
/**
*
*/
package tune.program.concurrent;
import java.util.concurrent.atomic.AtomicReference;
/**
* 使用Treiber算法实现Stack：基于CAS以及AtomicReference。
*
* @author yangwm Aug 25, 2010 10:50:17 AM
*/
public class ConcurrentStack<E> {
AtomicReference<Node<E>> head = new AtomicReference<Node<E>>();
public void push(E item) {
Node<E> newHead = new Node<E>(item);
Node<E> oldHead;
do {
oldHead = head.get();
newHead.next = oldHead;
} while (!head.compareAndSet(oldHead, newHead));
}
public E pop() {
Node<E> oldHead;
Node<E> newHead;
do {
oldHead = head.get();
if (oldHead == null) {
return null;
}
newHead = oldHead.next;
} while (!head.compareAndSet(oldHead, newHead));
return oldHead.item;
}
static class Node<E> {
final E item;
Node<E> next;
public Node(E item) {
this.item = item;
}
}
}
/**
*
*/
package tune.program.concurrent;
import java.util.Stack;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
/**
* 基准测试：Treiber算法实现Stack、同步实现的Stack
*
* @author yangwm Aug 25, 2010 11:36:14 AM
*/
public class StackBenchmark {
public static void main(String[] args) throws Exception {
StackBenchmark stackBenchmark = new StackBenchmark();
stackBenchmark.run();
}
private Stack<String> stack = new Stack<String>();
private ConcurrentStack<String> concurrentStack = new ConcurrentStack<String>();
private static final int THREAD_COUNT = 300;
private CountDownLatch latch = new CountDownLatch(THREAD_COUNT);
private CyclicBarrier barrier = new CyclicBarrier(THREAD_COUNT);
public void run() throws Exception {
StackTask stackTask = new StackTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(stackTask).start();
}
latch.await();
long endTime = System.currentTimeMillis();
System.out.println(“Stack consume Time: ” + (endTime - beginTime) + ” ms”);
latch = new CountDownLatch(THREAD_COUNT);
barrier = new CyclicBarrier(THREAD_COUNT);
ConcurrentStackTask concurrentStackTask = new ConcurrentStackTask();
beginTime = System.currentTimeMillis();
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(concurrentStackTask).start();
}
latch.await();
endTime = System.currentTimeMillis();
System.out.println(“ConcurrentStack consume Time: ” + (endTime - beginTime) + ” ms”);
}
class StackTask implements Runnable {
@Override
public void run() {
try {
barrier.await();
} catch (Exception e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
stack.push(Thread.currentThread().getName());
stack.pop();
}
latch.countDown();
}
}
class ConcurrentStackTask implements Runnable {
@Override
public void run() {
try {
barrier.await();
} catch (Exception e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
concurrentStack.push(Thread.currentThread().getName());
concurrentStack.pop();
}
latch.countDown();
}
}
}
/*
Stack consume Time: 94 ms
ConcurrentStack consume Time: 63 ms
Stack consume Time: 78 ms
ConcurrentStack consume Time: 62 ms
*/
寻找性能瓶颈
性能瓶颈的表象：资源消耗过多、外部处理系统的性能不足、资源消耗不多但程序的响应速度却仍达不到要求。
资源消耗：CPU、文件IO、网络IO、内存。
外部处理系统的性能不足：所调用的其他系统提供的功能或数据库操作的响应速度不够。
资源消耗不多但程序的响应速度却仍达不到要求：程序代码运行效率不够高、未充分使用资源、程序结构不合理。
CPU消耗分析
CPU主要用于中断、内核、用户进程的任务处理，优先级为中断>内核>用户进程。
上下文切换：
每个线程分配一定的执行时间，当到达执行时间、线程中有IO阻塞或高优先级线程要执行时，将切换执行的线程。在切换时要存储目前线程的执行状态，并恢复要执行的线程的状态。
对于Java应用，典型的是在进行文件IO操作、网络IO操作、锁等待、线程Sleep时，当前线程会进入阻塞或休眠状态，从而触发上下文切换，上下文切换过多会造成内核占据较多的CPU的使用。
运行队列：
每个CPU核都维护一个可运行的线程队列。系统的load主要由CPU的运行队列来决定。
运行队列值越大，就意味着线程会要消耗越长的时间才能执行完成。
利用率：
CPU在用户进程、内核、中断处理、IO等待、空闲，这五个部分使用百分比。
文件IO消耗分析
Linux在操作文件时，将数据放入文件缓存区，直到内存不够或系统要释放内存给用户进程使用。所以通常情况下只有写文件和第一次读取文件时会产生真正的文件IO。
对于Java应用，造成文件IO消耗高主要是多个线程需要进行大量内容写入（例如频繁的日志写入）的动作、磁盘设备本身的处理速度慢、文件系统慢、操作的文件本身已经很大。
网络IO消耗分析
对于分布式Java应用，网卡中断是不是均衡分配到各CPU(cat/proc/interrupts查看)。
内存消耗分析（-Xms和-Xmx设为相同的值，避免运行期JVM堆内存要不断申请内存）
对于Java应用，内存的消耗主要在Java堆内存上，只有创建线程和使用Direct ByteBuffer才会操作JVM堆外的内存。
JVM内存消耗过多会导致GC执行频繁，CPU消耗增加，应用线程的执行速度严重下降，甚至造成OutOfMemoryError，最终导致Java进程退出。
JVM堆外的内存
swap的消耗、物理内存的消耗、JVM内存的消耗。
程序执行慢原因分析
锁竞争激烈：很多线程竞争互斥资源，但资源有限， 造成其他线程都处于等待状态。
未充分使用硬件资源：线程操作被串行化。
数据量增长：单表数据量太大（如1个亿）造成数据库读写速度大幅下降（操作此表）。
调优
JVM调优（最关键参数为：-Xms -Xmx -Xmn -XX:SurvivorRatio
-XX:MaxTenuringThreshold）
代大小调优：避免新生代大小设置过小、避免新生代大小设置过大、避免Survivor设置过小或过大、合理设置新生代存活周期。
-Xmn
调整新生代大小，新生代越大通常也意味着更多对象会在minor GC阶段被回收，但可能有可能造成旧生代大小，造成频繁触发Full
GC，甚至是OutOfMemoryError。
-XX:SurvivorRatio调整Eden区与Survivor区的大小，Eden
区越大通常也意味着minor GC发生频率越低，但可能有可能造成Survivor区太小，导致对象minor
GC后就直接进入旧生代，从而更频繁触发Full GC。
GC策略的调优：CMS
GC多数动作是和应用并发进行的，确实可以减小GC动作给应用造成的暂停时间。对于Web应用非常需要一个对应用造成暂停时间短的GC，再加上Web应用
的瓶颈都不在CPU上，在G1还不够成熟的情况下，CMS GC是不错的选择。
（如果系统不是CPU密集型，且从新生代进入旧生代的大部分对象是可以回收的，那么采用CMS
GC可以更好地在旧生代满之前完成对象的回收，更大程度降低Full GC发生的可能）
在调整了内存管理方面的参数后应通过-XX:PrintGCDetails、-XX:+PrintGCTimeStamps、
-XX:+PrintGCApplicationStoppedTime以及jstat或visualvm等方式观察调整后的GC状况。
出内存管理以外的其他方面的调优参数：-XX:CompileThreshold、-XX:+UseFastAccessorMethods、
-XX:+UseBaiasedLocking。
程序调优
CPU消耗严重的解决方法
CPU us高的解决方法：
CPU us 高的原因主要是执行线程不需要任何挂起动作，且一直执行，导致CPU 没有机会去调度执行其他的线程。
调优方案： 增加Thread.sleep，以释放CPU 的执行权，降低CPU 的消耗。以损失单次执行性能为代价的，但由于其降低了CPU 的消耗，对于多线程的应用而言，反而提高了总体的平均性能。
（在实际的Java应用中类似场景， 对于这种场景最佳方式是改为采用wait/notify机制）
对于其他类似循环次数过多、正则、计算等造成CPU us过高的状况， 则需要结合业务调优。
对于GC频繁，则需要通过JVM调优或程序调优，降低GC的执行次数。
CPU sy高的解决方法：
CPU sy 高的原因主要是线程的运行状态要经常切换，对于这种情况，常见的一种优化方法是减少线程数。
调优方案： 将线程数降低
这种调优过后有可能会造成CPU us过高，所以合理设置线程数非常关键。
对于Java分布式应用，还有一种典型现象是应用中有较多的网络IO操作和确实需要一些锁竞争机制（如数据库连接池），但为了能够支撑搞得并发量，可采用协程（Coroutine）来支撑更高的并发量，避免并发量上涨后造成CPU sy消耗严重、系统load迅速上涨和系统性能下降。
在Java中实现协程的框架有Kilim，Kilim执行一项任务创建Task，使用Task的暂停机制，而不是Thread，Kilim承担了线程调度以及上下切换动作，Task相对于原生Thread而言就轻量级多了，且能更好利用CPU。Kilim带来的是线程使用率的提升，但同时由于要在JVM堆中保存Task上下文信息，因此在采用Kilim的情况下要消耗更多的内存。（目前JDK 7中也有一个支持协程方式的实现，另外基于JVM的Scala的Actor也可用于在Java使用协程）
文件IO消耗严重的解决方法
从程序的角度而言，造成文件IO消耗严重的原因主要是多个线程在写进行大量的数据到同一文件，导致文件很快变得很大，从而写入速度越来越慢，并造成各线程激烈争抢文件锁。
常用调优方法：
异步写文件
批量读写
限流
限制文件大小
网络IO消耗严重的解决方法
从程序的角度而言，造成网络IO消耗严重的原因主要是同时需要发送或接收的包太多。
常用调优方法：
限流，限流通常是限制发送packet的频率，从而在网络IO消耗可接受的情况下来发送packget。
内存消耗严重的解决方法
释放不必要的引用：代码持有了不需要的对象引用，造成这些对象无法被GC，从而占据了JVM堆内存。（使用ThreadLocal：注意在线程内动作执行完毕时，需执行ThreadLocal.set把对象清除，避免持有不必要的对象引用）
使用对象缓存池：创建对象要消耗一定的CPU以及内存，使用对象缓存池一定程度上可降低JVM堆内存的使用。
采用合理的缓存失效算法：如果放入太多对象在缓存池中，反而会造成内存的严重消耗， 同时由于缓存池一直对这些对象持有引用，从而造成Full GC增多，对于这种状况要合理控制缓存池的大小，避免缓存池的对象数量无限上涨。（经典的缓存失效算法来清除缓存池中的对象：FIFO、LRU、LFU等）
合理使用SoftReference和WeekReference：SoftReference的对象会在内存不够用的时候回收，WeekReference的对象会在Full GC的时候回收。
资源消耗不多但程序执行慢的情况的解决方法
降低锁竞争： 多线多了，锁竞争的状况会比较明显，这时候线程很容易处于等待锁的状况，从而导致性能下降以及CPU sy上升。
使用并发包中的类：大多数采用了lock-free、nonblocking算法。
使用Treiber算法：基于CAS以及AtomicReference。
使用Michael-Scott非阻塞队列算法：基于CAS以及AtomicReference，典型ConcurrentLindkedQueue。
（基于CAS和AtomicReference来实现无阻塞是不错的选择，但值得注意的是，lock-free算法需不断的循环比较来保证资源的一致性的，对于冲突较多的应用场景而言，会带来更高的CPU消耗，因此不一定采用CAS实现无阻塞的就一定比采用lock方式的性能好。 还有一些无阻塞算法的改进：MCAS、WSTM等）
尽可能少用锁：尽可能只对需要控制的资源做加锁操作（通常没有必要对整个方法加锁，尽可能让锁最小化，只对互斥及原子操作的地方加锁，加锁时尽可能以保护资源的最小化粒度为单位–如只对需要保护的资源加锁而不是this）。
拆分锁：独占锁拆分为多把锁（读写锁拆分、类似ConcurrentHashMap中默认拆分为16把锁），很多程度上能提高读写的性能，但需要注意在采用拆分锁后，全局性质的操作会变得比较复杂（如ConcurrentHashMap中size操作）。（拆分锁太多也会造成副作用，如CPU消耗明显增加）
去除读写操作的互斥：在修改时加锁，并复制对象进行修改，修改完毕后切换对象的引用，从而读取时则不加锁。这种称为CopyOnWrite，CopyOnWriteArrayList是典型实现，好处是可以明显提升读的性能，适合读多写少的场景， 但由于写操作每次都要复制一份对象，会消耗更多的内存。
充分利用硬件资源（CPU和内存）：
充分利用CPU
在能并行处理的场景中未使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）， 例如单线程的计算，可以拆分为多个线程分别计算，最后将结果合并，JDK 7中的fork-join框架。
Amdahl定律公式：1/(F+(1-F)/N)。
充分利用内存
数据的缓存、耗时资源的缓存（数据库连接创建、网络连接的创建等）、页面片段的缓存。
毕竟内存的读取肯定远快于硬盘、网络的读取， 在内存消耗可接受、GC频率、以及系统结构（例如集群环境可能会带来缓存的同步）可接受情况下，应充分利用内存来缓存数据，提升系统的性能。
总结：
好的调优策略是收益比（调优后提升的效果/调优改动所需付出的代价）最高的，通常来说简单的系统调优比较好做，因此尽量保持单机上应用的纯粹性， 这是大型系统的基本架构原则。
调优的三大有效原则：充分而不过分使用硬件资源、合理调整JVM、合理使用JDK包。
学习参考资料：
《分布式Java应用：基础与实践》
补充《分布式Java应用：基础与实践》一些代码样例：
cpu———————————–
CpuNotUseEffectiveDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.cpu;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
/**
* 未充分利用CPU：在能并行处理的场景中未使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）
*
* @author yangwm Aug 25, 2010 9:54:50 AM
*/
public class CpuNotUseEffectiveDemo {
private static int executeTimes = 10;
private static int taskCount = 200;
public static void main(String[] args) throws Exception {
Task task = new Task();
for (int i = 0; i < taskCount; i++) {
task.addTask(Integer.toString(i));
}
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
Thread thread = new Thread(task);
thread.start();
thread.join();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) TaskCount Per Round( ” + taskCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class Task implements Runnable {
List<String> tasks = new ArrayList<String>();
Random random = new Random();
boolean exitFlag = false;
public void addTask(String task) {
List<String> copyTasks = new ArrayList<String>(tasks);
copyTasks.add(task);
tasks = copyTasks;
}
@Override
public void run() {
List<String> runTasks = tasks;
List<String> removeTasks = new ArrayList<String>();
for (String task : runTasks) {
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
removeTasks.add(task);
}
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) TaskCount Per Round( 200 ) Execute Time ( 10687 ) ms
*/
/**
*
*/
package tune.program.cpu;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
/**
* 未充分利用CPU：在能并行处理的场景中未使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）
*
* @author yangwm Aug 25, 2010 9:54:50 AM
*/
public class CpuNotUseEffectiveDemo {
private static int executeTimes = 10;
private static int taskCount = 200;
public static void main(String[] args) throws Exception {
Task task = new Task();
for (int i = 0; i < taskCount; i++) {
task.addTask(Integer.toString(i));
}
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
Thread thread = new Thread(task);
thread.start();
thread.join();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) TaskCount Per Round( ” + taskCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class Task implements Runnable {
List<String> tasks = new ArrayList<String>();
Random random = new Random();
boolean exitFlag = false;
public void addTask(String task) {
List<String> copyTasks = new ArrayList<String>(tasks);
copyTasks.add(task);
tasks = copyTasks;
}
@Override
public void run() {
List<String> runTasks = tasks;
List<String> removeTasks = new ArrayList<String>();
for (String task : runTasks) {
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
removeTasks.add(task);
}
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) TaskCount Per Round( 200 ) Execute Time ( 10687 ) ms
*/
CpuUseEffectiveDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.cpu;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
/**
* 充分利用CPU：在能并行处理的场景中使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）
*
* @author yangwm Aug 25, 2010 9:54:50 AM
*/
public class CpuUseEffectiveDemo {
private static int executeTimes = 10;
private static int taskCount = 200;
private static final int TASK_THREADCOUNT = 16;
private static CountDownLatch latch;
public static void main(String[] args) throws Exception {
Task[] tasks = new Task[TASK_THREADCOUNT];
for (int i = 0; i < TASK_THREADCOUNT; i++) {
tasks[i] = new Task();
}
for (int i = 0; i < taskCount; i++) {
int mod = i % TASK_THREADCOUNT;
tasks[mod].addTask(Integer.toString(i));
}
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(TASK_THREADCOUNT);
for (int j = 0; j < TASK_THREADCOUNT; j++) {
Thread thread = new Thread(tasks[j]);
thread.start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) TaskCount Per Round( ” + taskCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class Task implements Runnable {
List<String> tasks = new ArrayList<String>();
Random random = new Random();
boolean exitFlag = false;
public void addTask(String task) {
List<String> copyTasks = new ArrayList<String>(tasks);
copyTasks.add(task);
tasks = copyTasks;
}
@Override
public void run() {
List<String> runTasks = tasks;
List<String> removeTasks = new ArrayList<String>();
for (String task : runTasks) {
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
removeTasks.add(task);
}
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
latch.countDown();
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) TaskCount Per Round( 200 ) Execute Time ( 938 ) ms
*/
/**
*
*/
package tune.program.cpu;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
/**
* 充分利用CPU：在能并行处理的场景中使用足够的线程（线程增加：CPU资源消耗可接受且不会带来激烈竞争锁的场景下）
*
* @author yangwm Aug 25, 2010 9:54:50 AM
*/
public class CpuUseEffectiveDemo {
private static int executeTimes = 10;
private static int taskCount = 200;
private static final int TASK_THREADCOUNT = 16;
private static CountDownLatch latch;
public static void main(String[] args) throws Exception {
Task[] tasks = new Task[TASK_THREADCOUNT];
for (int i = 0; i < TASK_THREADCOUNT; i++) {
tasks[i] = new Task();
}
for (int i = 0; i < taskCount; i++) {
int mod = i % TASK_THREADCOUNT;
tasks[mod].addTask(Integer.toString(i));
}
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(TASK_THREADCOUNT);
for (int j = 0; j < TASK_THREADCOUNT; j++) {
Thread thread = new Thread(tasks[j]);
thread.start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) TaskCount Per Round( ” + taskCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class Task implements Runnable {
List<String> tasks = new ArrayList<String>();
Random random = new Random();
boolean exitFlag = false;
public void addTask(String task) {
List<String> copyTasks = new ArrayList<String>(tasks);
copyTasks.add(task);
tasks = copyTasks;
}
@Override
public void run() {
List<String> runTasks = tasks;
List<String> removeTasks = new ArrayList<String>();
for (String task : runTasks) {
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
removeTasks.add(task);
}
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
latch.countDown();
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) TaskCount Per Round( 200 ) Execute Time ( 938 ) ms
*/
fileio——————————————————————-
IOWaitHighDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.fileio;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.util.Random;
/**
* 文件IO消耗严重的原因主要是多个线程在写进行大量的数据到同一文件，
* 导致文件很快变得很大，从而写入速度越来越慢，并造成各线程激烈争抢文件锁。
*
* @author yangwm Aug 21, 2010 9:48:34 PM
*/
public class IOWaitHighDemo {
private String fileName = “iowait.log”;
private static int threadCount = Runtime.getRuntime().availableProcessors();
private Random random = new Random();
public static void main(String[] args) throws Exception {
if (args.length == 1) {
threadCount = Integer.parseInt(args[1]);
}
IOWaitHighDemo demo = new IOWaitHighDemo();
demo.runTest();
}
private void runTest() throws Exception {
File file = new File(fileName);
file.createNewFile();
for (int i = 0; i < threadCount; i++) {
new Thread(new Task()).start();
}
}
class Task implements Runnable {
@Override
public void run() {
while (true) {
try {
StringBuilder strBuilder = new StringBuilder(“====begin====/n”);
String threadName = Thread.currentThread().getName();
for (int i = 0; i < 100000; i++) {
strBuilder.append(threadName);
strBuilder.append(”/n”);
}
strBuilder.append(”====end====/n”);
BufferedWriter writer = new BufferedWriter(new FileWriter(fileName, true));
writer.write(strBuilder.toString());
writer.close();
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
}
}
}
}
}
/*
C:/Documents and Settings/yangwm>jstack 2656
2010-08-21 23:24:17
Full thread dump Java HotSpot(TM) Client VM (17.0-b05 mixed mode):
”DestroyJavaVM” prio=6 tid=0x00868c00 nid=0xde0 waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
”Thread-1” prio=6 tid=0x0ab9dc00 nid=0xb7c runnable [0x0b0bf000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.close0(Native Method)
at java.io.FileOutputStream.close(FileOutputStream.java:336)
at sun.nio.cs.StreamEncoder.implClose(StreamEncoder.java:320)
at sun.nio.cs.StreamEncoder.close(StreamEncoder.java:149)
- locked <0x034dd268> (a java.io.FileWriter)
at java.io.OutputStreamWriter.close(OutputStreamWriter.java:233)
at java.io.BufferedWriter.close(BufferedWriter.java:265)
- locked <0x034dd268> (a java.io.FileWriter)
at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:58)</span> </span></li><li class=""><span><span class="comment"> at java.lang.Thread.run(Thread.java:717)</span> </span></li><li class="alt"><span><span class="comment">"Thread-0" prio=6 tid=0x0ab9d400 nid=0x80c runnable [0x0b06f000]</span> </span></li><li class=""><span><span class="comment"> java.lang.Thread.State: RUNNABLE</span> </span></li><li class="alt"><span><span class="comment"> at java.io.FileOutputStream.writeBytes(Native Method)</span> </span></li><li class=""><span><span class="comment"> at java.io.FileOutputStream.write(FileOutputStream.java:292)</span> </span></li><li class="alt"><span><span class="comment"> at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)</span> </span></li><li class=""><span><span class="comment"> at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:282)</span> </span></li><li class="alt"><span><span class="comment"> at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)</span> </span></li><li class=""><span><span class="comment"> - locked <0x034e1290> (a java.io.FileWriter)</span> </span></li><li class="alt"><span><span class="comment"> at java.io.OutputStreamWriter.write(OutputStreamWriter.java:207)</span> </span></li><li class=""><span><span class="comment"> at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:128)</span> </span></li><li class="alt"><span><span class="comment"> - locked <0x034e1290> (a java.io.FileWriter)</span> </span></li><li class=""><span><span class="comment"> at java.io.BufferedWriter.write(BufferedWriter.java:229)</span> </span></li><li class="alt"><span><span class="comment"> - locked <0x034e1290> (a java.io.FileWriter)</span> </span></li><li class=""><span><span class="comment"> at java.io.Writer.write(Writer.java:157)</span> </span></li><li class="alt"><span><span class="comment"> at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:58)
at java.lang.Thread.run(Thread.java:717)
"Thread-0" prio=6 tid=0x0ab9d400 nid=0x80c runnable [0x0b06f000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:292)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:282)
at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.OutputStreamWriter.write(OutputStreamWriter.java:207)
at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:128)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.BufferedWriter.write(BufferedWriter.java:229)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.Writer.write(Writer.java:157)
at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:57)
at java.lang.Thread.run(Thread.java:717)
”Low Memory Detector” daemon prio=6 tid=0x0ab6f800 nid=0xfb0 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
”CompilerThread0” daemon prio=10 tid=0x0ab6c800 nid=0x5fc waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
”Attach Listener” daemon prio=10 tid=0x0ab67800 nid=0x6fc waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
”Signal Dispatcher” daemon prio=10 tid=0x0ab66800 nid=0x5a0 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
”Finalizer” daemon prio=8 tid=0x0ab54000 nid=0xe74 in Object.wait() [0x0ac8f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)</span> </span></li><li class="alt"><span><span class="comment"> at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)</span> </span></li><li class=""><span><span class="comment"> - locked <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
- locked <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at java.lang.ref.FinalizerFinalizerThread.run(Finalizer.java:177)</span> </span></li><li class="alt"><span><span class="comment">"Reference Handler" daemon prio=10 tid=0x0ab4f800 nid=0x8a4 in Object.wait() [0x0ac3f000]</span> </span></li><li class=""><span><span class="comment"> java.lang.Thread.State: WAITING (on object monitor)</span> </span></li><li class="alt"><span><span class="comment"> at java.lang.Object.wait(Native Method)</span> </span></li><li class=""><span><span class="comment"> - waiting on <0x02f15af8> (a java.lang.ref.ReferenceFinalizerThread.run(Finalizer.java:177)
"Reference Handler" daemon prio=10 tid=0x0ab4f800 nid=0x8a4 in Object.wait() [0x0ac3f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x02f15af8> (a java.lang.ref.ReferenceLock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.ReferenceReferenceHandler.run(Reference.java:133)</span> </span></li><li class="alt"><span><span class="comment"> - locked <0x02f15af8> (a java.lang.ref.ReferenceReferenceHandler.run(Reference.java:133)
- locked <0x02f15af8> (a java.lang.ref.ReferenceLock)
”VM Thread” prio=10 tid=0x0ab4a800 nid=0x1d0 runnable
”VM Periodic Task Thread” prio=10 tid=0x0ab7d400 nid=0x464 waiting on condition
JNI global references: 693
C:/Documents and Settings/yangwm>
*/
/**
*
*/
package tune.program.fileio;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.util.Random;
/**
* 文件IO消耗严重的原因主要是多个线程在写进行大量的数据到同一文件，
* 导致文件很快变得很大，从而写入速度越来越慢，并造成各线程激烈争抢文件锁。
*
* @author yangwm Aug 21, 2010 9:48:34 PM
*/
public class IOWaitHighDemo {
private String fileName = “iowait.log”;
private static int threadCount = Runtime.getRuntime().availableProcessors();
private Random random = new Random();
public static void main(String[] args) throws Exception {
if (args.length == 1) {
threadCount = Integer.parseInt(args[1]);
}
IOWaitHighDemo demo = new IOWaitHighDemo();
demo.runTest();
}
private void runTest() throws Exception {
File file = new File(fileName);
file.createNewFile();
for (int i = 0; i < threadCount; i++) {
new Thread(new Task()).start();
}
}
class Task implements Runnable {
@Override
public void run() {
while (true) {
try {
StringBuilder strBuilder = new StringBuilder(“====begin====/n”);
String threadName = Thread.currentThread().getName();
for (int i = 0; i < 100000; i++) {
strBuilder.append(threadName);
strBuilder.append(“/n”);
}
strBuilder.append(“====end====/n”);
BufferedWriter writer = new BufferedWriter(new FileWriter(fileName, true));
writer.write(strBuilder.toString());
writer.close();
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
}
}
}
}
}
/*
C:/Documents and Settings/yangwm>jstack 2656
2010-08-21 23:24:17
Full thread dump Java HotSpot(TM) Client VM (17.0-b05 mixed mode):
“DestroyJavaVM” prio=6 tid=0x00868c00 nid=0xde0 waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
“Thread-1” prio=6 tid=0x0ab9dc00 nid=0xb7c runnable [0x0b0bf000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.close0(Native Method)
at java.io.FileOutputStream.close(FileOutputStream.java:336)
at sun.nio.cs.StreamEncoder.implClose(StreamEncoder.java:320)
at sun.nio.cs.StreamEncoder.close(StreamEncoder.java:149)
- locked <0x034dd268> (a java.io.FileWriter)
at java.io.OutputStreamWriter.close(OutputStreamWriter.java:233)
at java.io.BufferedWriter.close(BufferedWriter.java:265)
- locked <0x034dd268> (a java.io.FileWriter)
at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:58)atjava.lang.Thread.run(Thread.java:717)“Thread−0”prio=6tid=0x0ab9d400nid=0x80crunnable[0x0b06f000]java.lang.Thread.State:RUNNABLEatjava.io.FileOutputStream.writeBytes(NativeMethod)atjava.io.FileOutputStream.write(FileOutputStream.java:292)atsun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)atsun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:282)atsun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)−locked<0x034e1290>(ajava.io.FileWriter)atjava.io.OutputStreamWriter.write(OutputStreamWriter.java:207)atjava.io.BufferedWriter.flushBuffer(BufferedWriter.java:128)−locked<0x034e1290>(ajava.io.FileWriter)atjava.io.BufferedWriter.write(BufferedWriter.java:229)−locked<0x034e1290>(ajava.io.FileWriter)atjava.io.Writer.write(Writer.java:157)attune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:58)
at java.lang.Thread.run(Thread.java:717)
“Thread-0” prio=6 tid=0x0ab9d400 nid=0x80c runnable [0x0b06f000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:292)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:282)
at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.OutputStreamWriter.write(OutputStreamWriter.java:207)
at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:128)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.BufferedWriter.write(BufferedWriter.java:229)
- locked <0x034e1290> (a java.io.FileWriter)
at java.io.Writer.write(Writer.java:157)
at tune.IOWaitHighDemoTask.run(IOWaitHighDemo.java:57)
at java.lang.Thread.run(Thread.java:717)
“Low Memory Detector” daemon prio=6 tid=0x0ab6f800 nid=0xfb0 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
“CompilerThread0” daemon prio=10 tid=0x0ab6c800 nid=0x5fc waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
“Attach Listener” daemon prio=10 tid=0x0ab67800 nid=0x6fc waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
“Signal Dispatcher” daemon prio=10 tid=0x0ab66800 nid=0x5a0 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
“Finalizer” daemon prio=8 tid=0x0ab54000 nid=0xe74 in Object.wait() [0x0ac8f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)atjava.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)−locked<0x02f15d90>(ajava.lang.ref.ReferenceQueueLock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
- locked <0x02f15d90> (a java.lang.ref.ReferenceQueueLock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at java.lang.ref.FinalizerFinalizerThread.run(Finalizer.java:177)“ReferenceHandler”daemonprio=10tid=0x0ab4f800nid=0x8a4inObject.wait()[0x0ac3f000]java.lang.Thread.State:WAITING(onobjectmonitor)atjava.lang.Object.wait(NativeMethod)−waitingon<0x02f15af8>(ajava.lang.ref.ReferenceFinalizerThread.run(Finalizer.java:177)
“Reference Handler” daemon prio=10 tid=0x0ab4f800 nid=0x8a4 in Object.wait() [0x0ac3f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x02f15af8> (a java.lang.ref.ReferenceLock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.ReferenceReferenceHandler.run(Reference.java:133)−locked<0x02f15af8>(ajava.lang.ref.ReferenceReferenceHandler.run(Reference.java:133)
- locked <0x02f15af8> (a java.lang.ref.ReferenceLock)
“VM Thread” prio=10 tid=0x0ab4a800 nid=0x1d0 runnable
“VM Periodic Task Thread” prio=10 tid=0x0ab7d400 nid=0x464 waiting on condition
JNI global references: 693
C:/Documents and Settings/yangwm>
*/
LogControl
[java] view plaincopyprint?/**
*
*/
package tune.program.fileio;
import java.util.concurrent.atomic.AtomicInteger;
/**
* 日志控制：采用简单策略为统计一段时间内日志输出频率， 当超出这个频率时，一段时间内不再写log
*
* @author yangwm Aug 24, 2010 10:41:43 AM
*/
public class LogControl {
public static void main(String[] args) {
for (int i = 1; i <= 1000; i++) {
if (LogControl.isLog()) {
//logger.error(errorInfo, throwable);
System.out.println(”errorInfo ” + i);
}
//
if (i % 100 == 0) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
private static final long INTERVAL = 1000;
private static final long PUNISH_TIME = 5000;
private static final int ERROR_THRESHOLD = 100;
private static AtomicInteger count = new AtomicInteger(0);
private static long beginTime;
private static long punishTimeEnd;
// 由于控制不用非常精确， 因此忽略此处的并发问题
public static boolean isLog() {
//System.out.println(count.get() + ”, ” + beginTime + ”, ” + punishTimeEnd + ”, ” + System.currentTimeMillis());
// 不写日志阶段
if (punishTimeEnd > 0 && punishTimeEnd > System.currentTimeMillis()) {
return false;
}
// 重新计数
if (count.getAndIncrement() == 0) {
beginTime = System.currentTimeMillis();
return true;
} else { // 已在计数
// 超过阀门值， 设置count为0并设置一段时间内不写日志
if (count.get() > ERROR_THRESHOLD) {
count.set(0);
punishTimeEnd = PUNISH_TIME + System.currentTimeMillis();
return false;
}
// 没超过阀门值， 且当前时间已超过计数周期，则重新计算
else if (System.currentTimeMillis() > (beginTime + INTERVAL)) {
count.set(0);
}
return true;
}
}
}
/*
errorInfo 1
errorInfo 2
……
errorInfo 99
errorInfo 100
errorInfo 601
errorInfo 602
……
errorInfo 699
errorInfo 700
*/
/**
*
*/
package tune.program.fileio;
import java.util.concurrent.atomic.AtomicInteger;
/**
* 日志控制：采用简单策略为统计一段时间内日志输出频率， 当超出这个频率时，一段时间内不再写log
*
* @author yangwm Aug 24, 2010 10:41:43 AM
*/
public class LogControl {
public static void main(String[] args) {
for (int i = 1; i <= 1000; i++) {
if (LogControl.isLog()) {
//logger.error(errorInfo, throwable);
System.out.println(“errorInfo ” + i);
}
//
if (i % 100 == 0) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
private static final long INTERVAL = 1000;
private static final long PUNISH_TIME = 5000;
private static final int ERROR_THRESHOLD = 100;
private static AtomicInteger count = new AtomicInteger(0);
private static long beginTime;
private static long punishTimeEnd;
// 由于控制不用非常精确， 因此忽略此处的并发问题
public static boolean isLog() {
//System.out.println(count.get() + “, ” + beginTime + “, ” + punishTimeEnd + “, ” + System.currentTimeMillis());
// 不写日志阶段
if (punishTimeEnd > 0 && punishTimeEnd > System.currentTimeMillis()) {
return false;
}
// 重新计数
if (count.getAndIncrement() == 0) {
beginTime = System.currentTimeMillis();
return true;
} else { // 已在计数
// 超过阀门值， 设置count为0并设置一段时间内不写日志
if (count.get() > ERROR_THRESHOLD) {
count.set(0);
punishTimeEnd = PUNISH_TIME + System.currentTimeMillis();
return false;
}
// 没超过阀门值， 且当前时间已超过计数周期，则重新计算
else if (System.currentTimeMillis() > (beginTime + INTERVAL)) {
count.set(0);
}
return true;
}
}
}
/*
errorInfo 1
errorInfo 2
……
errorInfo 99
errorInfo 100
errorInfo 601
errorInfo 602
……
errorInfo 699
errorInfo 700
*/
memory——————————————————————-
MemoryHighDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.memory;
import java.nio.ByteBuffer;
/**
* direct bytebuffer消耗的是jvm堆外的内存，但同样是基于GC方式来释放的。
*
* @author yangwm Aug 21, 2010 9:40:18 PM
*/
public class MemoryHighDemo {
public static void main(String[] args) throws Exception{
Thread.sleep(20000);
System.out.println(”read to create bytes,so jvm heap will be used”);
byte[] bytes=new byte[128*1000*1000];
bytes[0]=1;
bytes[1]=2;
Thread.sleep(10000);
System.out.println(”read to allocate & put direct bytebuffer,no jvm heap should be used”);
ByteBuffer buffer=ByteBuffer.allocateDirect(128*1024*1024);
buffer.put(bytes);
buffer.flip();
Thread.sleep(10000);
System.out.println(”ready to gc,jvm heap will be freed”);
bytes=null;
System.gc();
Thread.sleep(10000);
System.out.println(”read to get bytes,then jvm heap will be used”);
byte[] resultbytes=new byte[128*1000*1000];
buffer.get(resultbytes);
System.out.println(”resultbytes[1] is: ”+resultbytes[1]);
Thread.sleep(10000);
System.out.println(”read to gc all”);
buffer=null;
resultbytes=null;
System.gc();
Thread.sleep(10000);
}
}
/*
D:/study/tempProject/JavaLearn/classes>java -Xms140M -Xmx140M tune.MemoryHighDemo
read to create bytes,so jvm heap will be used
read to allocate & put direct bytebuffer,no jvm heap should be used
ready to gc,jvm heap will be freed
read to get bytes,then jvm heap will be used
resultbytes[1] is: 2
read to gc all
*/
/**
*
*/
package tune.program.memory;
import java.nio.ByteBuffer;
/**
* direct bytebuffer消耗的是jvm堆外的内存，但同样是基于GC方式来释放的。
*
* @author yangwm Aug 21, 2010 9:40:18 PM
*/
public class MemoryHighDemo {
public static void main(String[] args) throws Exception{
Thread.sleep(20000);
System.out.println(“read to create bytes,so jvm heap will be used”);
byte[] bytes=new byte[128*1000*1000];
bytes[0]=1;
bytes[1]=2;
Thread.sleep(10000);
System.out.println(“read to allocate & put direct bytebuffer,no jvm heap should be used”);
ByteBuffer buffer=ByteBuffer.allocateDirect(128*1024*1024);
buffer.put(bytes);
buffer.flip();
Thread.sleep(10000);
System.out.println(“ready to gc,jvm heap will be freed”);
bytes=null;
System.gc();
Thread.sleep(10000);
System.out.println(“read to get bytes,then jvm heap will be used”);
byte[] resultbytes=new byte[128*1000*1000];
buffer.get(resultbytes);
System.out.println(“resultbytes[1] is: “+resultbytes[1]);
Thread.sleep(10000);
System.out.println(“read to gc all”);
buffer=null;
resultbytes=null;
System.gc();
Thread.sleep(10000);
}
}
/*
D:/study/tempProject/JavaLearn/classes>java -Xms140M -Xmx140M tune.MemoryHighDemo
read to create bytes,so jvm heap will be used
read to allocate & put direct bytebuffer,no jvm heap should be used
ready to gc,jvm heap will be freed
read to get bytes,then jvm heap will be used
resultbytes[1] is: 2
read to gc all
*/
ObjectCachePool
[java] view plaincopyprint?/**
*
*/
package tune.program.memory;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
/**
* 采用合理的缓存失效算法: FIFO、LRU、LFU等
*
* @author yangwm Aug 24, 2010 6:06:48 PM
*/
public class ObjectCachePool<K, V> {
public static void main(String[] args) {
// FIFO_POLICY
int size = 10;
int policy = 1;
ObjectCachePool<Integer, Integer> objectCachePool = new ObjectCachePool<Integer, Integer>(size, policy);
for (int i = 1; i <= 15; i++) {
objectCachePool.put(i, i);
}
for (int i = 15; i >= 1; i–) {
objectCachePool.put(i, i);
}
System.out.println(”size(“ + size + “), policy(“ + policy + “) FIFO ”);
for (Map.Entry<Integer, Integer> entry : objectCachePool.entrySet()) {
System.out.println(entry.getKey() + ”, ” + entry.getValue());
}
// LRU_POLICY
size = 10;
policy = 2;
objectCachePool = new ObjectCachePool<Integer, Integer>(size, policy);
for (int i = 1; i <= 15; i++) {
objectCachePool.put(i, i);
}
for (int i = 15; i >= 1; i–) {
objectCachePool.put(i, i);
}
System.out.println(”size(“ + size + “), policy(“ + policy + “) LRU ”);
for (Map.Entry<Integer, Integer> entry : objectCachePool.entrySet()) {
System.out.println(entry.getKey() + ”, ” + entry.getValue());
}
}
private static final int FIFO_POLICY = 1;
private static final int LRU_POLICY = 2;
private static final int DEFAULT_SIZE = 10;
private Map<K, V> cacheObjects;
public ObjectCachePool() {
this(DEFAULT_SIZE);
}
public ObjectCachePool(int size) {
this(size, FIFO_POLICY);
}
public ObjectCachePool(final int size, final int policy) {
switch (policy) {
case FIFO_POLICY:
cacheObjects = new LinkedHashMap<K, V>(size) {
/**
*
*/
private static final long serialVersionUID = 1L;
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > size;
}
};
break;
case LRU_POLICY:
cacheObjects = new LinkedHashMap<K, V>(size, 0.75f, true) {
/**
*
*/
private static final long serialVersionUID = 1L;
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > size;
}
};
break;
default:
throw new IllegalArgumentException(“Unknown policy: ” + policy);
}
}
public void put(K key, V value) {
cacheObjects.put(key, value);
}
public void get(K key) {
cacheObjects.get(key);
}
public void remove(K key) {
cacheObjects.remove(key);
}
public void clear() {
cacheObjects.clear();
}
public Set<Map.Entry<K, V>> entrySet() {
return cacheObjects.entrySet();
}
}
/*
size(10), policy(1) FIFO
11, 11
12, 12
13, 13
14, 14
15, 15
5, 5
4, 4
3, 3
2, 2
1, 1
size(10), policy(2) LRU
10, 10
9, 9
8, 8
7, 7
6, 6
5, 5
4, 4
3, 3
2, 2
1, 1
*/
/**
*
*/
package tune.program.memory;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
/**
* 采用合理的缓存失效算法: FIFO、LRU、LFU等
*
* @author yangwm Aug 24, 2010 6:06:48 PM
*/
public class ObjectCachePool<K, V> {
public static void main(String[] args) {
// FIFO_POLICY
int size = 10;
int policy = 1;
ObjectCachePool<Integer, Integer> objectCachePool = new ObjectCachePool<Integer, Integer>(size, policy);
for (int i = 1; i <= 15; i++) {
objectCachePool.put(i, i);
}
for (int i = 15; i >= 1; i–) {
objectCachePool.put(i, i);
}
System.out.println(“size(” + size + “), policy(” + policy + “) FIFO “);
for (Map.Entry<Integer, Integer> entry : objectCachePool.entrySet()) {
System.out.println(entry.getKey() + “, ” + entry.getValue());
}
// LRU_POLICY
size = 10;
policy = 2;
objectCachePool = new ObjectCachePool<Integer, Integer>(size, policy);
for (int i = 1; i <= 15; i++) {
objectCachePool.put(i, i);
}
for (int i = 15; i >= 1; i–) {
objectCachePool.put(i, i);
}
System.out.println(“size(” + size + “), policy(” + policy + “) LRU “);
for (Map.Entry<Integer, Integer> entry : objectCachePool.entrySet()) {
System.out.println(entry.getKey() + “, ” + entry.getValue());
}
}
private static final int FIFO_POLICY = 1;
private static final int LRU_POLICY = 2;
private static final int DEFAULT_SIZE = 10;
private Map<K, V> cacheObjects;
public ObjectCachePool() {
this(DEFAULT_SIZE);
}
public ObjectCachePool(int size) {
this(size, FIFO_POLICY);
}
public ObjectCachePool(final int size, final int policy) {
switch (policy) {
case FIFO_POLICY:
cacheObjects = new LinkedHashMap<K, V>(size) {
/**
*
*/
private static final long serialVersionUID = 1L;
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > size;
}
};
break;
case LRU_POLICY:
cacheObjects = new LinkedHashMap<K, V>(size, 0.75f, true) {
/**
*
*/
private static final long serialVersionUID = 1L;
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > size;
}
};
break;
default:
throw new IllegalArgumentException(“Unknown policy: ” + policy);
}
}
public void put(K key, V value) {
cacheObjects.put(key, value);
}
public void get(K key) {
cacheObjects.get(key);
}
public void remove(K key) {
cacheObjects.remove(key);
}
public void clear() {
cacheObjects.clear();
}
public Set<Map.Entry<K, V>> entrySet() {
return cacheObjects.entrySet();
}
}
/*
size(10), policy(1) FIFO
11, 11
12, 12
13, 13
14, 14
15, 15
5, 5
4, 4
3, 3
2, 2
1, 1
size(10), policy(2) LRU
10, 10
9, 9
8, 8
7, 7
6, 6
5, 5
4, 4
3, 3
2, 2
1, 1
*/
ObjectPoolDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.memory;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
/**
* 使用对象缓存池：创建对象要消耗一定的CPU以及内存，使用对象缓存池一定程度上可降低JVM堆内存的使用。
*
* @author yangwm Aug 24, 2010 4:34:47 PM
*/
public class ObjectPoolDemo {
private static int executeTimes = 10;
private static int maxFactor = 10;
private static int threadCount = 100;
private static final int NOTUSE_OBJECTPOOL = 1;
private static final int USE_OBJECTPOOL = 2;
private static int runMode = NOTUSE_OBJECTPOOL;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
Task task = new Task();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) Thread Per Round( ” + threadCount
+ ” ) Object Factor ( ” + maxFactor + “ ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class Task implements Runnable {
@Override
public void run() {
for (int j = 0; j < maxFactor; j++) {
if (runMode == USE_OBJECTPOOL) {
BigObjectPool.getInstance().getBigObject(j);
} else {
new BigObject(j);
}
}
latch.countDown();
}
}
static class BigObjectPool {
private static final BigObjectPool self = new BigObjectPool();
private final Map<Integer, BigObject> cacheObjects = new HashMap<Integer, BigObject>();
private BigObjectPool() {
}
public static BigObjectPool getInstance() {
return self;
}
public BigObject getBigObject(int factor) {
if (cacheObjects.containsKey(factor)) {
return cacheObjects.get(factor);
} else {
BigObject object = new BigObject(factor);
cacheObjects.put(factor, object);
return object;
}
}
}
static class BigObject {
private byte[] bytes = null;
public BigObject(int factor) {
bytes = new byte[(factor + 1) * 1024 * 1024];
}
public byte[] getBytes() {
return bytes;
}
}
}
/*
-Xms128M -Xmx128M -Xmn64M , runMode is NOTUSE_OBJECTPOOL:
Round: 1
……
Execute summary: Round( 10 ) Thread Per Round( 100 ) Object Factor ( 10 ) Execute Time ( 50672 ) ms
-Xms128M -Xmx128M -Xmn64M , runMode is USE_OBJECTPOOL:
Round: 1
……
Execute summary: Round( 10 ) Thread Per Round( 100 ) Object Factor ( 10 ) Execute Time ( 344 ) ms
*/
/**
*
*/
package tune.program.memory;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
/**
* 使用对象缓存池：创建对象要消耗一定的CPU以及内存，使用对象缓存池一定程度上可降低JVM堆内存的使用。
*
* @author yangwm Aug 24, 2010 4:34:47 PM
*/
public class ObjectPoolDemo {
private static int executeTimes = 10;
private static int maxFactor = 10;
private static int threadCount = 100;
private static final int NOTUSE_OBJECTPOOL = 1;
private static final int USE_OBJECTPOOL = 2;
private static int runMode = NOTUSE_OBJECTPOOL;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
Task task = new Task();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) Thread Per Round( ” + threadCount
+ ” ) Object Factor ( ” + maxFactor + ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class Task implements Runnable {
@Override
public void run() {
for (int j = 0; j < maxFactor; j++) {
if (runMode == USE_OBJECTPOOL) {
BigObjectPool.getInstance().getBigObject(j);
} else {
new BigObject(j);
}
}
latch.countDown();
}
}
static class BigObjectPool {
private static final BigObjectPool self = new BigObjectPool();
private final Map<Integer, BigObject> cacheObjects = new HashMap<Integer, BigObject>();
private BigObjectPool() {
}
public static BigObjectPool getInstance() {
return self;
}
public BigObject getBigObject(int factor) {
if (cacheObjects.containsKey(factor)) {
return cacheObjects.get(factor);
} else {
BigObject object = new BigObject(factor);
cacheObjects.put(factor, object);
return object;
}
}
}
static class BigObject {
private byte[] bytes = null;
public BigObject(int factor) {
bytes = new byte[(factor + 1) * 1024 * 1024];
}
public byte[] getBytes() {
return bytes;
}
}
}
/*
-Xms128M -Xmx128M -Xmn64M , runMode is NOTUSE_OBJECTPOOL:
Round: 1
……
Execute summary: Round( 10 ) Thread Per Round( 100 ) Object Factor ( 10 ) Execute Time ( 50672 ) ms
-Xms128M -Xmx128M -Xmn64M , runMode is USE_OBJECTPOOL:
Round: 1
……
Execute summary: Round( 10 ) Thread Per Round( 100 ) Object Factor ( 10 ) Execute Time ( 344 ) ms
*/
ThreadLocalDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.memory;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* 释放不必要的引用：代码持有了不需要的对象引用，造成这些对象无法被GC，从而占据了JVM堆内存。
* （使用ThreadLocal：注意在线程内动作执行完毕时，需执行 ThreadLocal.set把对象清除，避免持有不必要的对象引用）
*
* @author yangwm Aug 24, 2010 11:29:59 AM
*/
public class ThreadLocalDemo {
public static void main(String[] args) {
ThreadLocalDemo demo = new ThreadLocalDemo();
demo.run();
}
public void run() {
ExecutorService executor = Executors.newFixedThreadPool(1);
executor.execute(new Task());
System.gc();
}
class Task implements Runnable {
@Override
public void run() {
ThreadLocal<byte[]> localString = new ThreadLocal<byte[]>();
localString.set(new byte[1024 * 1024 * 30]);
// 业务逻辑
//localString.set(null); // 释放不必要的引用
}
}
}
/**
*
*/
package tune.program.memory;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* 释放不必要的引用：代码持有了不需要的对象引用，造成这些对象无法被GC，从而占据了JVM堆内存。
* （使用ThreadLocal：注意在线程内动作执行完毕时，需执行 ThreadLocal.set把对象清除，避免持有不必要的对象引用）
*
* @author yangwm Aug 24, 2010 11:29:59 AM
*/
public class ThreadLocalDemo {
public static void main(String[] args) {
ThreadLocalDemo demo = new ThreadLocalDemo();
demo.run();
}
public void run() {
ExecutorService executor = Executors.newFixedThreadPool(1);
executor.execute(new Task());
System.gc();
}
class Task implements Runnable {
@Override
public void run() {
ThreadLocal<byte[]> localString = new ThreadLocal<byte[]>();
localString.set(new byte[1024 * 1024 * 30]);
// 业务逻辑
//localString.set(null); // 释放不必要的引用
}
}
}
concurrent———————————————————————–
LockHotDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 锁竞争的状况会比较明显，这时候线程很容易处于等待锁的状况，从而导致性能下降以及CPU sy上升
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class LockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private final Lock lock = new ReentrantLock();
private Handler() {
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
try {
lock.lock();
// execute sth
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
lock.unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 10625 ) ms
*/
/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 锁竞争的状况会比较明显，这时候线程很容易处于等待锁的状况，从而导致性能下降以及CPU sy上升
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class LockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private final Lock lock = new ReentrantLock();
private Handler() {
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
try {
lock.lock();
// execute sth
try {
Thread.sleep(random.nextInt(10));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
lock.unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 10625 ) ms
*/
ReduceLockHotDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 尽可能少用锁：尽可能只对需要控制的资源做加锁操作
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class ReduceLockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private final Lock lock = new ReentrantLock();
private Handler() {
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
// execute sth don’t need lock
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
try {
lock.lock();
// execute sth
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
lock.unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 5547 ) ms
*/
/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 尽可能少用锁：尽可能只对需要控制的资源做加锁操作
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class ReduceLockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private final Lock lock = new ReentrantLock();
private Handler() {
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
// execute sth don’t need lock
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
try {
lock.lock();
// execute sth
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
lock.unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 5547 ) ms
*/
SplitReduceLockHotDemo
[java] view plaincopyprint?/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 尽可能少用锁：尽可能只对需要控制的资源做加锁操作
* 拆分锁：独占锁拆分为多把锁（读写锁拆分、类似ConcurrentHashMap中默认拆分为16把锁）
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class SplitReduceLockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(”Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(”Execute summary: Round( ” + executeTimes + “ ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + “ ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private int lockCount = 10;
private Lock[] locks = new Lock[lockCount];
private Handler() {
for (int i = 0; i < lockCount; i++) {
locks[i] = new ReentrantLock();
}
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
// execute sth don’t need lock
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
int mod = id % lockCount;
try {
locks[mod].lock();
// execute sth
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
locks[mod].unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 843 ) ms
*/
/**
*
*/
package tune.program.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 尽可能少用锁：尽可能只对需要控制的资源做加锁操作
* 拆分锁：独占锁拆分为多把锁（读写锁拆分、类似ConcurrentHashMap中默认拆分为16把锁）
*
* @author yangwm Aug 24, 2010 11:59:35 PM
*/
public class SplitReduceLockHotDemo {
private static int executeTimes = 10;
private static int threadCount = Runtime.getRuntime().availableProcessors() * 100;
private static CountDownLatch latch = null;
public static void main(String[] args) throws Exception {
HandleTask task = new HandleTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < executeTimes; i++) {
System.out.println(“Round: ” + (i + 1));
latch = new CountDownLatch(threadCount);
for (int j = 0; j < threadCount; j++) {
new Thread(task).start();
}
latch.await();
}
long endTime = System.currentTimeMillis();
System.out.println(“Execute summary: Round( ” + executeTimes + ” ) Thread Per Round( ” + threadCount
+ ” ) Execute Time ( ” + (endTime - beginTime) + ” ) ms”);
}
static class HandleTask implements Runnable {
private final Random random = new Random();
@Override
public void run() {
Handler.getInstance().handle(random.nextInt(10000));
latch.countDown();
}
}
static class Handler {
private static final Handler self = new Handler();
private final Random random = new Random();
private int lockCount = 10;
private Lock[] locks = new Lock[lockCount];
private Handler() {
for (int i = 0; i < lockCount; i++) {
locks[i] = new ReentrantLock();
}
}
public static Handler getInstance() {
return self;
}
public void handle(int id) {
// execute sth don’t need lock
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
int mod = id % lockCount;
try {
locks[mod].lock();
// execute sth
try {
Thread.sleep(random.nextInt(5));
} catch (Exception e) {
e.printStackTrace();
}
} finally {
locks[mod].unlock();
}
}
}
}
/*
Round: 1
……
Round: 10
Execute summary: Round( 10 ) Thread Per Round( 200 ) Execute Time ( 843 ) ms
*/
ConcurrentStack和StackBenchmark
[java] view plaincopyprint?/**
*
*/
package tune.program.concurrent;
import java.util.concurrent.atomic.AtomicReference;
/**
* 使用Treiber算法实现Stack：基于CAS以及AtomicReference。
*
* @author yangwm Aug 25, 2010 10:50:17 AM
*/
public class ConcurrentStack<E> {
AtomicReference<Node<E>> head = new AtomicReference<Node<E>>();
public void push(E item) {
Node<E> newHead = new Node<E>(item);
Node<E> oldHead;
do {
oldHead = head.get();
newHead.next = oldHead;
} while (!head.compareAndSet(oldHead, newHead));
}
public E pop() {
Node<E> oldHead;
Node<E> newHead;
do {
oldHead = head.get();
if (oldHead == null) {
return null;
}
newHead = oldHead.next;
} while (!head.compareAndSet(oldHead, newHead));
return oldHead.item;
}
static class Node<E> {
final E item;
Node<E> next;
public Node(E item) {
this.item = item;
}
}
}
/**
*
*/
package tune.program.concurrent;
import java.util.Stack;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
/**
* 基准测试：Treiber算法实现Stack、同步实现的Stack
*
* @author yangwm Aug 25, 2010 11:36:14 AM
*/
public class StackBenchmark {
public static void main(String[] args) throws Exception {
StackBenchmark stackBenchmark = new StackBenchmark();
stackBenchmark.run();
}
private Stack<String> stack = new Stack<String>();
private ConcurrentStack<String> concurrentStack = new ConcurrentStack<String>();
private static final int THREAD_COUNT = 300;
private CountDownLatch latch = new CountDownLatch(THREAD_COUNT);
private CyclicBarrier barrier = new CyclicBarrier(THREAD_COUNT);
public void run() throws Exception {
StackTask stackTask = new StackTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(stackTask).start();
}
latch.await();
long endTime = System.currentTimeMillis();
System.out.println(”Stack consume Time: ” + (endTime - beginTime) + “ ms”);
latch = new CountDownLatch(THREAD_COUNT);
barrier = new CyclicBarrier(THREAD_COUNT);
ConcurrentStackTask concurrentStackTask = new ConcurrentStackTask();
beginTime = System.currentTimeMillis();
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(concurrentStackTask).start();
}
latch.await();
endTime = System.currentTimeMillis();
System.out.println(”ConcurrentStack consume Time: ” + (endTime - beginTime) + “ ms”);
}
class StackTask implements Runnable {
@Override
public void run() {
try {
barrier.await();
} catch (Exception e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
stack.push(Thread.currentThread().getName());
stack.pop();
}
latch.countDown();
}
}
class ConcurrentStackTask implements Runnable {
@Override
public void run() {
try {
barrier.await();
} catch (Exception e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
concurrentStack.push(Thread.currentThread().getName());
concurrentStack.pop();
}
latch.countDown();
}
}
}
/*
Stack consume Time: 94 ms
ConcurrentStack consume Time: 63 ms
Stack consume Time: 78 ms
ConcurrentStack consume Time: 62 ms
*/
/**
*
*/
package tune.program.concurrent;
import java.util.concurrent.atomic.AtomicReference;
/**
* 使用Treiber算法实现Stack：基于CAS以及AtomicReference。
*
* @author yangwm Aug 25, 2010 10:50:17 AM
*/
public class ConcurrentStack<E> {
AtomicReference<Node<E>> head = new AtomicReference<Node<E>>();
public void push(E item) {
Node<E> newHead = new Node<E>(item);
Node<E> oldHead;
do {
oldHead = head.get();
newHead.next = oldHead;
} while (!head.compareAndSet(oldHead, newHead));
}
public E pop() {
Node<E> oldHead;
Node<E> newHead;
do {
oldHead = head.get();
if (oldHead == null) {
return null;
}
newHead = oldHead.next;
} while (!head.compareAndSet(oldHead, newHead));
return oldHead.item;
}
static class Node<E> {
final E item;
Node<E> next;
public Node(E item) {
this.item = item;
}
}
}
/**
*
*/
package tune.program.concurrent;
import java.util.Stack;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
/**
* 基准测试：Treiber算法实现Stack、同步实现的Stack
*
* @author yangwm Aug 25, 2010 11:36:14 AM
*/
public class StackBenchmark {
public static void main(String[] args) throws Exception {
StackBenchmark stackBenchmark = new StackBenchmark();
stackBenchmark.run();
}
private Stack<String> stack = new Stack<String>();
private ConcurrentStack<String> concurrentStack = new ConcurrentStack<String>();
private static final int THREAD_COUNT = 300;
private CountDownLatch latch = new CountDownLatch(THREAD_COUNT);
private CyclicBarrier barrier = new CyclicBarrier(THREAD_COUNT);
public void run() throws Exception {
StackTask stackTask = new StackTask();
long beginTime = System.currentTimeMillis();
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(stackTask).start();
}
latch.await();
long endTime = System.currentTimeMillis();
System.out.println(“Stack consume Time: ” + (endTime - beginTime) + ” ms”);
latch = new CountDownLatch(THREAD_COUNT);
barrier = new CyclicBarrier(THREAD_COUNT);
ConcurrentStackTask concurrentStackTask = new ConcurrentStackTask();
beginTime = System.currentTimeMillis();
for (int i = 0; i < THREAD_COUNT; i++) {
new Thread(concurrentStackTask).start();
}
latch.await();
endTime = System.currentTimeMillis();
System.out.println(“ConcurrentStack consume Time: ” + (endTime - beginTime) + ” ms”);
}
class StackTask implements Runnable {
@Override
public void run() {
try {
barrier.await();
} catch (Exception e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
stack.push(Thread.currentThread().getName());
stack.pop();
}
latch.countDown();
}
}
class ConcurrentStackTask implements Runnable {
@Override
public void run() {
try {
barrier.await();
} catch (Exception e) {
e.printStackTrace();
}
for (int i = 0; i < 10; i++) {
concurrentStack.push(Thread.currentThread().getName());
concurrentStack.pop();
}
latch.countDown();
}
}
}
/*
Stack consume Time: 94 ms
ConcurrentStack consume Time: 63 ms
Stack consume Time: 78 ms
ConcurrentStack consume Time: 62 ms
*/
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