标签:java target tle soc jit 日志 sem err topic
查看Java代码对应的汇编指令又一利器,JITWatch
纠错 13 May 2015
接着上一篇文章 查看Java代码对应的汇编指令利器,hsdis 。JITWatch提供了更好的显示方式,还有各种图表,称得上又一利器。
github地址: JITWatch
git clone git@github.com:AdoptOpenJDK/jitwatch.git
cd jitwatch
mvn clean install -DskipTests=true
./launchUI.sh
我们通过一个简单的例子来看下如何使用(例子稍微复杂些,为了了解JDK8对AtomicInteger.getAndIncrement()方法做的优化),基于JDK8(jdk7的getAndIncrement()方法实现不同)
首先给出java代码,AtomicInteger_jdk8.java
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;
public class AtomicInteger_jdk8 {
private final static int TEST_SIZE = 100000000;
private final static int THREAD_COUNT = 10;
private CountDownLatch cdl = new CountDownLatch(THREAD_COUNT + 1);
private AtomicInteger ai = new AtomicInteger(0);
private long startTime;
public void init() {
startTime = System.nanoTime();
}
public class MyTask implements Runnable {
@Override
public void run() {
while (true) {
if(ai.getAndIncrement() == TEST_SIZE) {
System.out.println(System.nanoTime() - startTime);
cdl.countDown();
System.exit(0);
}
}
}
}
public static void main(String[] args) {
AtomicInteger_jdk8 at = new AtomicInteger_jdk8();
at.init();
for (int n = 0; n < THREAD_COUNT; n++)
new Thread(at.new MyTask()).start();
System.out.println("start");
at.cdl.countDown();
}
}
编译执行,并输出日志(提示:需要hsdis)
javac AtomicInteger_jdk8.java
java -server -XX:+UnlockDiagnosticVMOptions -XX:+TraceClassLoading -XX:+PrintAssembly -XX:+LogCompilation -XX:LogFile=jit.log AtomicInteger_jdk8
如图所示:
AtomicInteger.getAndIncrement()方法对应的汇编指令callq。
通过JITWatch发现,getAndAddInt()已经被编译为特殊的机器指令xadd(这就是为啥jdk8比jdk7快的原因,读者可以自己看下jdk7是啥)
--------------------------------------------补充下JDK7的------------------------------------
查看Java代码对应的汇编指令又一利器,JITWatch 转
标签:java target tle soc jit 日志 sem err topic
原文地址:http://www.cnblogs.com/zengkefu/p/6910341.html