heidsoft-paas / concurrent

Java Concurrent Programming

Java Concurrent Programming

并发编程

Java 4.0

• 1.原子操作 synchronized

• 2.锁 synchronized

• 3.线程协作

  • wait | notity
  • suspend | resume
  • yield | join
  • stop | destroy

Java 5.0

• 1.原子操作 java.util.concurrent.atomic

• 2.锁 java.util.concurrent.locks

• 3.线程协作 java.util.concurrent

并发编程分享提纲

• 1.线程

  • 1.1 State

    • new
    • runnable
    • wait
    • time_wait
    • blocked
    • terminated

  • 1.2 Interrupt 中断

  • 1.3 Thread Communication:

    • Semaphore 信号量
    • CountDownLatch 倒数同步
    • Exchanger 线程数据交换
    • CyclicBarrier 多路线程同步等待
    • Phaser fork/join同步等待

• 2.同步源语

  • 2.1
    • volatile
    • synchronized

• 3.锁

  • Reentrantlock

  • ReentrantReadWriteLock

• 4.并发容器

  • 4.1 concurrent collection:

    • ConcurrentLinedQuere
    • ConcurrentHashMap
    • *ConcurrentSkipListMap
    • *ConcurrentSkipListSet
    • *ConcurrentTransferQueue

  • 4.2 BlockingQueue

    • ArrayBlockingQueue 数组构成的有界阻塞队列
    • LinkedBlockingQueue 链表构成的有界阻塞队列
    • LinkedBlockingDeque 链表结构的双端阻塞队列
    • PriorityBlockingQueue 支持优先级排序的无界阻塞队列
    • DelayQueue 使用优先级队列实现的无界阻塞队列
    • SynchronousQueue 不存储元素的阻塞队列
    • LinkedTransferQueue 链表结构的无界阻塞队列

  • 4.3

    • CopyOnWriteXXX

• 5.线程池

  • ThreadPoolExecutor
  • ScheduledThreadPoolExecutor

• 6.模式

  • 窃取工作模式
  • 缓存一致性协议

• 7.其它知识

  • 线程池经验

    • CPU密集型任务配置尽可能小的线程，如配置N*CPU+1个线程的线程池。

    • IO密集型任务则由于线程并不是一直在执行任务，则配置尽可能多的线程，如2NCPU。

    • 混合型的任务则将其拆分成一个CPU密集型任务和一个IO密集型任务，前提是这两个任务执行的时间相差不是太大，那么分解后执行的吞吐率要高于串行执行的吞吐率。 *并发编程

    • 线程通信问题 (JMM控制)

    • 线程同步问题

    • 堆中(共享变量)：实例变量、静态变量、数组

    • 栈中(私有变量)：

      • 局部变量(Local variables)、
      • 异常处理器参数(exception handler parameters)、
      • 方法定义参数(formal method parameters)

    • main memory

    • local memory 抽象概念:抽象了缓存、写缓冲区、寄存器、以及硬件和编译优化

    • 重排序：提高性能 编译器和处理器会做重排序

      • 1.编译器优化
      • 2.指令级并行重排序(Instruction-Level Parallelism， ILP) 现代处理器
      • 3.内存系统重排序 (处理器使用了缓存和读写缓冲区)

  • happens-before

    • Program order rule. Each action in a thread happens-before every action in that thread that comes later in the program order. (程序次序规则：在一个单独的线程中，按照程序代码的执行流顺序，(时间上)先执行的操作happen—before(时间上)后执行的操作。)

    • Monitor lock rule. An unlock on a monitor lock happens-before every subsequent lock on that same monitor lock. (管理锁定规则：一个unlock操作happen—before后面(时间上的先后顺序，下同)对同一个锁的lock操作。)

    • Volatile variable rule. A write to a volatile field happens-before every subsequent read of that same field. (volatile变量规则：对一个volatile变量的写操作happen—before后面对该变量的读操作。)

    • Thread start rule. A call to Thread.start on a thread happens-before every action in the started thread. (线程启动规则：Thread对象的start()方法happen—before此线程的每一个动作。)

    • Thread termination rule. Any action in a thread happens-before any other thread detects that thread has terminated, either by successfully return from Thread.join or by Thread.isAlive returning false. (线程终止规则：线程的所有操作都happen—before对此线程的终止检测，可以通过Thread.join()方法结束、Thread.isAlive()的返回值等手段检测到线程已经终止执行。)

    • Interruption rule. A thread calling interrupt on another thread happens-before the interrupted thread detects the interrupt (either by having InterruptedException tHRown, or invoking isInterrupted or interrupted). (线程中断规则：对线程interrupt()方法的调用happen—before发生于被中断线程的代码检测到中断时事件的发生。)

    • Finalizer rule. The end of a constructor for an object happens-before the start of the finalizer for that object. (对象终结规则：一个对象的初始化完成(构造函数执行结束)happen—before它的finalize()方法的开始。)

    • Transitivity. If A happens-before B, and B happens-before C, then A happens-before C. (传递性：如果操作A happen—before操作B，操作B happen—before操作C，那么可以得出A happen—before操作C。)