Java环形缓冲区+生产消费模型及同步开销测试

代码是为了使用环形缓冲区实现消费者生产者功能:

package ringBuffer.parallel;import java.io.IOException;import java.io.RandomAccessFile;import java.util.LinkedHashMap;import java.util.Map;public class Producer { public static void main(String[] args) {long start = System.currentTimeMillis() ;Producer mc = new Producer() ;Consumer cr = mc.new Consumer() ;cr.start() ;for (Integer j = 0; j < 5; j++) {LinkedHashMap<Integer, String> msgs = new LinkedHashMap<Integer, String>() ;for (Integer i = 0; i < 100000; i++) {msgs.put(i,j.toString()) ;}cr.addToMsgBuf(msgs);}try {//cr.waitUntilEmpty();cr.interrupt() ;cr.join() ;   //这里主线程会否比子线程先跑完? 加上join} catch (InterruptedException e) {e.printStackTrace();}System.out.println(" last : "+ ( System.currentTimeMillis() -start));System.exit(0);}class Consumer extends Thread {int bufferSize = 2 * 1024 * 1024;private byte[] buffer = new byte[bufferSize];private Integer pos = 0;private Integer prePos = 0;String outputFile = "F:\\test\\ringBuf.txt";    RandomAccessFile raf;    StringBuffer sb = null;    LinkedHashMap<Integer, String> cMsgs = new LinkedHashMap<Integer, String>() ;    ;public Consumer(){    try {    raf = new RandomAccessFile(outputFile, "rw");} catch (IOException e) {e.printStackTrace();}}public void run() {try {   while (!Thread.interrupted()) {   synchronized (cMsgs){   while (cMsgs.isEmpty()) {   cMsgs.wait();               }   sb = new StringBuffer();   for (Map.Entry<Integer, String> v : cMsgs.entrySet()) {   sb.append(v.getKey()).append("-").append(v.getValue()).append("V") ;   }   cMsgs.clear() ;   cMsgs.notify() ;   }   sb.append("S");     byte[] buf = sb.toString().getBytes();   int length = buf.length ;   pos = prePos + length ;   int bufPos = 0;   if (pos > bufferSize && prePos < bufferSize) {       bufPos = bufferSize - prePos;System.arraycopy(buf, 0, buffer, prePos, bufPos);  prePos = pos = 0;long fileLength = raf.length();  raf.seek(fileLength);  raf.write(buffer);     }else     System.arraycopy(buf, 0, buffer, prePos, length);     if(bufPos==0){      prePos = pos;   }else{       System.arraycopy(buf, bufPos, buffer, prePos, length-bufPos);    prePos = prePos +  length-bufPos ;   pos =prePos ;   }   }   long fileLength = raf.length();     raf.seek(fileLength);     raf.write(buffer, 0, prePos);     raf.close();    }catch (IOException e) {e.printStackTrace();} catch (InterruptedException e) {e.printStackTrace();}  }public void addToMsgBuf(LinkedHashMap<Integer, String> currentStepMsgs) { synchronized (cMsgs) { try {     while(!cMsgs.isEmpty()){     cMsgs.wait() ;     }     cMsgs.putAll(currentStepMsgs); cMsgs.notify() ;} catch (InterruptedException e) {e.printStackTrace();}     }}public void waitUntilEmpty() throws InterruptedException{synchronized (cMsgs) { while(!cMsgs.isEmpty()){  cMsgs.wait(); }        }}}}

package ringBuffer.parallel;import java.io.IOException;import java.io.RandomAccessFile;public class Producer2 { public static void main(String[] args) {long start = System.currentTimeMillis() ;Producer2 pr = new Producer2() ;Consumer cr = pr.new Consumer() ;cr.start() ;for (Integer j = 0; j < 5; j++) {StringBuffer sb = new StringBuffer();for (Integer i = 0; i < 100000; i++) {sb.append(i.toString()).append("-").append(j.toString() + "V");}sb.append("S");byte[] msgs = sb.toString().getBytes();//System.out.println(msgs.length);cr.addToMsgBuf(msgs);}try {cr.interrupt() ; cr.join() ;  //这里主线程会否比子线程先跑完? 加上join} catch (InterruptedException e) {e.printStackTrace();}System.out.println(" last : "+ ( System.currentTimeMillis() -start));}class Consumer extends Thread {int bufferSize = 2 * 1024 * 1024;private byte[] buffer = new byte[bufferSize];private Integer pos = 0;private Integer prePos = 0;String outputFile = "F:\\test\\ringBuf.txt";        private int totalLength = 0;    RandomAccessFile raf;public Consumer(){    try {    raf = new RandomAccessFile(outputFile, "rw");} catch (IOException e) {e.printStackTrace();}}public void run() {try {while (!Thread.interrupted()) {synchronized (buffer) {while (pos > bufferSize ) { totalLength = totalLength + prePos ;    long fileLength = raf.length();         raf.seek(fileLength);         raf.write(buffer) ;  prePos = prePos % bufferSize ;pos = prePos;  buffer.notify() ;   }}}totalLength = totalLength + prePos ;long fileLength = raf.length();        raf.seek(fileLength);        raf.write(buffer, 0, prePos) ;  raf.close() ;} catch (IOException e) {e.printStackTrace();}}public void addToMsgBuf(byte[] buf) {if (buf == null || buf.length == 0)return;try {synchronized (buffer) {pos = prePos + buf.length ;int bufPos = 0 ;while (pos > bufferSize && prePos<bufferSize) {  bufPos = bufferSize-prePos ;System.arraycopy(buf, 0, buffer, prePos, bufPos);  prePos = bufferSize;System.out.println("Wait Until there is enough space! ");buffer.wait();}System.arraycopy(buf,bufPos, buffer, prePos, buf.length - bufPos);prePos = pos ;if(pos==0&&pos==prePos){  //当buffer写满时prePos = prePos + (buf.length - bufPos) ;pos = prePos ;}}} catch (InterruptedException e) {e.printStackTrace();}}}}

 

以上两种实现方式，从代码功能上看，两者差不多，

空间开销分析:

从理论上看，Producer比Producer2多使用了 new LinkedHashMap<Integer, String>() ;    可能导致比其多占用内存，但实际测试显示， Producer2比Producer内存的占用略高，使用jdk自带的Jconsole(两者均为0次gc收集时)，Producer2的堆上已使用内存较高(同一个程序不同次执行时堆内存的使用情况不同，因此需要均为0次gc时比较)，

从YongGc Times(没有发生oldGc)看，也是Producer2明显多( jstat -gc pid interval(ms) 次数 > 1.txt   Producer2为289次,远高于Producer的114次，这是我在内存较小的机器上的测试结果，换成大内存机器后，两者的YGC次数相同，均为6次)，

时间开销分析:

时间上猜测原因是由于Producer并行粒度太小，  

  producer2直接写环形缓冲区(写缓冲区时同步一次)，  而producer 数据先写入map(每次循环同步一次)，再到缓冲区

 这里用了int指针代替空的判断，提高了性能.

我机器配置为

为了使结果明显区别，我将main中的j 改为10:

Producer: 

 last : 544

Producer2:

Wait Until there is enough space! 
 last : 426

这里加上直接用顺序实现的，发现同步的开销确实很大，因此环形缓冲区适用于内存不足的情形，且同步开销真是大啊！

package Producer;import java.io.IOException;import java.io.RandomAccessFile;public class ProduceSeq {public static void main(String[] args) {long start = System.currentTimeMillis() ;StringBuffer sb = new StringBuffer();for (Integer j = 0; j < 10; j++) {for (Integer i = 0; i < 100000; i++) {sb.append(i.toString()).append("-").append(j.toString() + "V");}sb.append("S");}     try {    RandomAccessFile raf = new RandomAccessFile("F:\\test\\ringBuf.txt", "rw");    raf.write(sb.toString().getBytes());    raf.close() ; } catch (IOException e) {e.printStackTrace(); }System.out.println(" last : "+ ( System.currentTimeMillis() -start));}}

 last : 317

此外，对cuda的同步实现和java做了比较，发现cuda只有共享存储等简单的同步方式(函数)，没有java这种更高级的锁的实现方式处理数据一致性。