Scala Worker Actor的设计注意事项
Scala Worker Actor的设计注意事项
提问于 2012-09-04 00:20:10
今年秋天我要上一门分布式系统的课，因为Scala参与者在这方面表现得非常有用，所以我刚刚开始学习Scala。从我从“Actors in Scala”文本中读到的关于Actors的内容来看，我有一个问题，这个问题在文本中似乎没有被很清楚地解决。
我目前正在一台具有多核处理器的单机上对我的程序进行建模，并在Master-Workers模型中使用基于事件的参与者。现在，在以下两种设计选择中，哪一种可以使所有处理器核心都得到最佳利用？
1)将演员的数量限制在一个小的固定数量，而不管主演员有多少工作要分配给工人演员(顺便说一句，有时可能相当大)
2)生成与Master Actor需要完成的作业数量一样多的Actor
对于上述两个选择，哪些因素会左右我的决定？
更新:我打印出了我正在运行的100个工人角色的线程ids，下面是输出-
No. of Processors-2
MainActor is on thread:Thread[ForkJoinPool-1-worker-0,5,main]
AccumulatorActor is on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-1 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-4 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-5 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-6 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-7 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-8 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-9 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-10 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-3 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-12 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-13 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-14 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-15 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-2 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-16 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-11 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-17 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-18 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-19 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-20 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-21 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-22 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-23 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-24 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-25 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-26 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-28 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-29 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-27 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-30 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-31 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-33 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-32 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-34 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-35 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-36 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-38 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-39 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-40 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-41 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-42 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-43 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-44 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-45 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-46 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-47 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-48 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-51 running on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-50 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-54 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-49 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-56 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-57 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-58 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-55 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-59 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-52 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-61 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-60 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-63 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-53 running on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-65 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-66 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-68 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-64 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-62 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-70 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-69 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-67 running on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-72 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-73 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-71 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-75 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-78 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-79 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-80 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-81 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-82 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-83 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-74 running on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-84 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-85 running on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-77 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-76 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-86 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-87 running on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-88 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-89 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-91 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-92 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-94 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-95 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]
Worker Actor-96 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-90 running on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-98 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-99 running on thread:Thread[ForkJoinPool-1-worker-1,5,main]
Worker Actor-100 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-93 running on thread:Thread[ForkJoinPool-1-worker-2,5,main]
Worker Actor-37 running on thread:Thread[ForkJoinPool-1-worker-0,5,main]
Worker Actor-97 running on thread:Thread[ForkJoinPool-1-worker-3,5,main]从上面可以看出，在ForkJoinPool中有四个工作线程在运行，而我的机器上有两个cpu核心。我不确定这是为什么，因为快速查看ResizableThreadPoolScheduler的源代码使我相信，最初池中的工作线程的数量等于cpu核心的数量，并且在任何参与者在池中的某个工作线程上被阻塞的情况下，这些数量是动态增加的。我使用的所有参与者都是基于事件(React)的，并且不执行任何阻塞操作。理想的情况是在ForkJoinPool中只有2个线程，并让它们在执行每个参与者的工作的两个核心上并行运行。我对此的理解是正确的，还是我在这里遗漏了什么？
回答 1
Stack Overflow用户
回答已采纳
发布于 2012-09-04 03:20:55
你听起来像是在想演员，就像他们是线一样。拥有参与者系统的部分目的是将你的问题与参与者本身解耦。创建演员的成本很低，所以有几千个演员是很好的。拥有数千个演员并不意味着他们每个人都会尝试同时运行。
Scheduler负责管理如何执行参与者请求。默认情况下，您将获得一个ForkJoinScheduler或(在异常JVM上) ResizableThreadPoolScheduler
在这两种情况下，并行任务的数量都由ThreadPoolConfig控制，并且默认为max(2*cores,4)。在这个类中，您还可以看到如何通过系统属性覆盖这些默认值：
actors.enableForkJoin允许您控制scheduleractors.corePoolSize设置的选择初始“线程”池sizeactors.maxPoolSize设置最大大小
请注意，研究Akka角色可能是一个更好的想法，因为他们可能会在某个时候replace the original Scala actor implementation，提供更多功能，并强制更干净地遵守角色模型(因为您只能获得ActorRef，不能再直接调用actor上的方法)。在Akka中，相当于调度器的是dispatchers。
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原文链接：
https://stackoverflow.com/questions/12251293
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