分析Java中的线程行为

Question

我需要画出两个并发运行的线程的写入访问图。将这些访问的时间戳值对写入数组的最佳方式是什么，而不会干扰线程本身？正在写入的队列看起来像这样：

import java.util.concurrent.atomic.AtomicInteger; 

class IQueue<T> { 
    AtomicInteger head = new AtomicInteger(0); 
    AtomicInteger tail = new AtomicInteger(0); 
    T[] items = (T[]) new Object[100]; 

    public void enq(T x) { 
     int slot; 
     do { 
      slot = tail.get(); 
     } while (! tail.compareAndSet(slot, slot+1)); 
     items[slot] = x; 
    } 

    public T deq() throws EmptyException { 
     T value; 
     int slot; 
     do { 
      slot = head.get(); 
      value = items[slot]; 
      if (value == null) 
       throw new EmptyException(); 
     } while (! head.compareAndSet(slot, slot+1)); 
     return value; 
    } 

    public String toString() { 
     String s = ""; 
     for (int i = head.get(); i < tail.get(); i++) { 
      s += items[i].toString() + "; "; 
     } 
     return s; 
    } 
} 

我想记录线程何时开始/停止写入。

Answer 1

对于正在运行的Java程序的动态（字节码）工具类，一种可能性是使用BTrace。
BTrace将追踪操作插入正在运行的Java程序的类中，并热插拔跟踪的程序类。

// import all BTrace annotations 
import com.sun.btrace.annotations.*; 
// import statics from BTraceUtils class 
import static com.sun.btrace.BTraceUtils.*; 

// @BTrace annotation tells that this is a BTrace program 
@BTrace 
public class HelloWorld { 

    // @OnMethod annotation tells where to probe. 
    // In this example, we are interested in entry 
    // into the Thread.start() method. 
    @OnMethod(
     clazz="java.lang.Thread", 
     method="start" 
    ) 
    public static void func() { 
     // println is defined in BTraceUtils 
     // you can only call the static methods of BTraceUtils 
     println("about to start a thread!"); 
    } 
}