MultiThreadingStudy/Docs/Jupyter笔记.2.4.线程本地存储.ipynb

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   "source": [
    "线程本地存储\n",
    "============================== "
   ]
  },
  {
   "attachments": {},
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   "metadata": {},
   "source": [
    "线程本地存储(Thread Local Storge,简称TLS)机制用于实现按线程隔离的线程本地变量，对于同一个线程本地变量，各个线程分别有独立的值，修改的值只能修改的线程可见。  <br/>\n",
    "\n",
    "线程要地存储可以分为原生实现与托管实现，原生实现指的是调用操作系统提供的接口访问原生线程对应的线程本地存储，而托管实现指的是调用.net提供的接口访问托管线程对应的线程本地存储。  <br/>\n",
    "\n",
    "原生实现，在Windows和linux上的实现不同，但同样都是调用系统提供的接口。  <br/>\n",
    "\n",
    "注意：线程本地存储目的是每线程复制一份数据，做到线程独立与隔离，而不是使用共享数据与同步(使用与同步实现在原子操作、锁、信号量等方面)。"
   ]
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   "metadata": {},
   "source": [
    "## 全局设置，语言设置、Nuget包引用、空间引用等"
   ]
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   "source": [
    "//全局设置\n",
    "#!csharp\n",
    "using System.Threading;\n",
    "using System.Threading.Channels;\n",
    "using System.Threading.Tasks;\n",
    "\n",
    "//全局变量\n",
    "var noteBookThreadDesc = \"NoteBook线程\";\n",
    "\n",
    "//全局方法\n",
    "//显示线程信息\n",
    "public void ShowThreadInfo(Thread showThread=null, string describe = null)\n",
    "{\n",
    "    if(showThread == null)\n",
    "    {\n",
    "        showThread = Thread.CurrentThread;\n",
    "    }\n",
    "\n",
    "    if(string.IsNullOrWhiteSpace(describe))\n",
    "    {\n",
    "        describe = showThread.Name == null ? \"无名\" : showThread.Name;\n",
    "    }\n",
    "\n",
    "    Console.WriteLine($\"{describe}线程ID：{showThread.ManagedThreadId} \");\n",
    "    Console.WriteLine($\"{describe}线程名：{showThread.Name} \");\n",
    "    Console.WriteLine($\"{describe}线程状态：{showThread.ThreadState} \");\n",
    "    Console.WriteLine($\"{describe}线程模式：{showThread.GetApartmentState()} \");\n",
    "    Console.WriteLine($\"{describe}激活：{(showThread.IsAlive ? \"活动\" : \"非活动\")} \");\n",
    "    Console.WriteLine($\"{describe}线程池线程：{(showThread.IsThreadPoolThread ? \"是的\" : \"否\")} \");\n",
    "    Console.WriteLine($\"{describe}后台线：{(showThread.IsBackground ? \"是的\" : \"不是\")} \");\n",
    "    Console.WriteLine($\"{describe}区域：{showThread.CurrentCulture}\");\n",
    "    Console.WriteLine($\"{describe}UI区域：{showThread.CurrentUICulture}\");\n",
    "    Console.WriteLine($\"{describe}优先级：{showThread.Priority}\");\n",
    "}\n",
    "\n",
    "//显示线程状态\n",
    "public void ShowThreadState(Thread showThread=null, string describe = null)\n",
    "{\n",
    "    if(showThread == null)\n",
    "    {\n",
    "        showThread = Thread.CurrentThread;\n",
    "    }\n",
    "\n",
    "    if(string.IsNullOrWhiteSpace(describe))\n",
    "    {\n",
    "        describe = showThread.Name == null ? \"无名\" : showThread.Name;\n",
    "    }\n",
    "    Console.WriteLine($\"{describe}线程状态：{showThread.ThreadState} \");\n",
    "}"
   ]
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   "source": [
    "## ThreadStatic Attribute 特性 实现"
   ]
  },
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   "metadata": {},
   "source": [
    "在 .NET 中标记了[ThreadStatic]特性的全局变量就是托管线程本地变量。  <br/>\n",
    "\n",
    "在 .NET 中，每个托管对象都关联一个TLB(Thread Local Block)表，TLB表以 AppDomain ID 为索引保存 TLM(Thread Local Module)表，TLM表以模块ID为索引保存托管线程本地存储空间的开始地址。当 .NET 运行时加载一个程序集时，会枚举程序集中的模块与模块中的全局变量，然后按是否线程本地变量分成两部分，非线程本地变量会保存在 AppDomain 对应的高频堆中；而线程本地变量只计算偏移值，存储空间会在首次访问时分配。 "
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   "source": [
    "注意：ThreadStatic 特性，只支持静态字段，不支持实例字段(实例字段不启作用)。"
   ]
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     "name": "stdout",
     "output_type": "stream",
     "text": [
      "计算结果：210\n",
      "计算结果：210\n",
      "210\n",
      "30 31 30 31 31 30 31 30 30 30 31 30 30 31 30\n"
     ]
    }
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   "source": [
    "///<summary>\n",
    "/// 无\"ThreadStatic\"特性：关键点是因为对共享变量Total的操作(++ -- += *=)不是原子性的\n",
    "/// 多线程时，可能会交叉执行，造成线程不安全。线程本地变量是使共享对象在每个线程都复制一份，做倒线程独立、互不影响。也可以使用原子操作代替，形成无锁算法。\n",
    "///</sumary>\n",
    "public class Demo\n",
    "{\n",
    "    //[ThreadStatic]\n",
    "    public static double Total = 0;\n",
    "    public static List<int> threadIds = new List<int>();\n",
    "    public double Sum()\n",
    "    {\n",
    "        //double temp = 0;\n",
    "        for (int i = 1; i <= 10; i++)\n",
    "        {\n",
    "            //temp = Total;\n",
    "            //关键点：这里的 += 不是原子操作，相当于 先\"加\"再\"赋值\"\n",
    "            Total += i;\n",
    "\n",
    "            double tem = Total + i;\n",
    "            Total = tem;\n",
    "            \n",
    "            threadIds.Add(Thread.CurrentThread.ManagedThreadId);\n",
    "            Thread.Sleep(100);\n",
    "\n",
    "            //Console.WriteLine($\"线程{Thread.CurrentThread.ManagedThreadId.ToString(\"000\")}: {temp.ToString(\"00000000\")} + {i.ToString(\"00000000\")} = {Total}\");\n",
    "        }\n",
    "        Console.WriteLine($\"计算结果：{Total}\");\n",
    "        return Total;\n",
    "    }\n",
    "}\n",
    "\n",
    "Demo.Total =100;\n",
    "var demo1 = new Demo();\n",
    "var thread_a = new Thread(()=>demo1.Sum());\n",
    "var thread_b = new Thread(()=>demo1.Sum());\n",
    "\n",
    "thread_a.Start();\n",
    "thread_b.Start();\n",
    "    \n",
    "thread_a.Join();\n",
    "thread_b.Join();\n",
    "\n",
    "//主线程（内核）调用类的静态字段\n",
    "Console.WriteLine(Demo.Total);\n",
    "\n",
    "Console.WriteLine($\"{string.Join(\" \",Demo.threadIds)}\");\n"
   ]
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   "source": [
    "## 数据槽 实现"
   ]
  },
  {
   "attachments": {},
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## ThreadLocal<T> 泛型类 实现"
   ]
  }
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