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15
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1 using System;
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2 using System.Collections.Generic;
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3 using System.Linq;
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4 using System.Text;
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5 using System.Threading;
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6 using System.Diagnostics;
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7
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8 namespace Implab.Parallels {
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9 public abstract class DispatchPool<TUnit> : IDisposable {
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10 readonly int m_minThreads;
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11 readonly int m_maxThreads;
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20
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12 int m_createdThreads = 0;
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13 int m_activeThreads = 0;
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14 int m_sleepingThreads = 0;
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15
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15 int m_maxRunningThreads = 0;
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16 int m_exitRequired = 0;
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20
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17 int m_releaseTimeout = 100; // timeout while the working thread will wait for the new tasks before exit
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15
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18 AutoResetEvent m_hasTasks = new AutoResetEvent(false);
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19
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20 protected DispatchPool(int min, int max) {
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21 if (min < 0)
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22 throw new ArgumentOutOfRangeException("min");
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23 if (max <= 0)
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24 throw new ArgumentOutOfRangeException("max");
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25
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26 if (min > max)
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27 min = max;
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28 m_minThreads = min;
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29 m_maxThreads = max;
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30 }
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31
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32 protected DispatchPool(int threads)
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33 : this(threads, threads) {
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34 }
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35
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36 protected DispatchPool() {
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37 int maxThreads, maxCP;
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38 ThreadPool.GetMaxThreads(out maxThreads, out maxCP);
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39
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40 m_minThreads = 0;
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41 m_maxThreads = maxThreads;
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42 }
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43
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44 protected void InitPool() {
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45 for (int i = 0; i < m_minThreads; i++)
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46 StartWorker();
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47 }
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48
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20
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49 public int PoolSize {
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50 get {
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51 return m_createdThreads;
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52 }
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53 }
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54
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55 public int ActiveThreads {
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56 get {
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57 return m_activeThreads;
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58 }
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59 }
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60
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61 public int MaxRunningThreads {
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62 get {
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63 return m_maxRunningThreads;
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64 }
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65 }
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66
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67 protected bool IsDisposed {
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68 get {
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69 return m_exitRequired != 0;
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70 }
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71 }
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72
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17
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73 protected abstract bool TryDequeue(out TUnit unit);
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74
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75 protected virtual bool ExtendPool() {
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76 if (m_sleepingThreads == 0)
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77 // no sleeping workers are available
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78 // try create one
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79 return StartWorker();
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80 else {
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81 // we can get here a race condition when several threads asks to extend pool
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82 // and some sleaping threads are exited due timeout but they are still counted as sleeping
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83 // in that case all of this threads could exit except one
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84 WakePool();
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85 return true;
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20
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86 }
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87
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17
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88 }
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89
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90 /// <summary>
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91 /// Запускает либо новый поток, если раньше не было ни одного потока, либо устанавливает событие пробуждение одного спящего потока
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92 /// </summary>
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93 protected void WakePool() {
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94 m_hasTasks.Set(); // wake sleeping thread;
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95
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96 if (AllocateThreadSlot(1)) {
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97 // if there were no threads in the pool
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98 var worker = new Thread(this.Worker);
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99 worker.IsBackground = true;
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100 worker.Start();
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101 }
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102 }
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103
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20
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104 bool Sleep(int timeout) {
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105 Interlocked.Increment(ref m_sleepingThreads);
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106 var result = m_hasTasks.WaitOne(timeout);
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107 Interlocked.Decrement(ref m_sleepingThreads);
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108 return result;
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109 }
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110
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111 protected virtual bool Suspend() {
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112 //no tasks left, exit if the thread is no longer needed
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113 bool last;
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114 bool requestExit;
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115
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116 if (m_releaseTimeout > 0)
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117 requestExit = !Sleep(m_releaseTimeout);
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118 else
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119 requestExit = true;
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120
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121
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122 if (requestExit && ReleaseThreadSlot(out last)) {
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123 // in case at the moment the last thread was being released
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124 // a new task was added to the queue, we need to try
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125 // to revoke the thread to avoid the situation when the task is left unprocessed
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126 if (last && m_hasTasks.WaitOne(0)) {
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127 if (AllocateThreadSlot(1))
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128 return true; // spin again...
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129 else
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130 // we failed to reallocate the first slot for this thread
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131 // therefore we need to release the event
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132 m_hasTasks.Set();
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133 }
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134
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135 return false;
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136 }
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137
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138 Sleep(-1);
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139
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140 return true;
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17
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141 }
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142
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143 #region thread slots traits
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144
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145 bool AllocateThreadSlot() {
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146 int current;
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147 // use spins to allocate slot for the new thread
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148 do {
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149 current = m_createdThreads;
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150 if (current >= m_maxThreads || m_exitRequired != 0)
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151 // no more slots left or the pool has been disposed
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152 return false;
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20
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153 } while (current != Interlocked.CompareExchange(ref m_createdThreads, current + 1, current));
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154
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155 UpdateMaxThreads(current + 1);
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156
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157 return true;
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158 }
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159
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160 bool AllocateThreadSlot(int desired) {
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161 if (desired - 1 != Interlocked.CompareExchange(ref m_createdThreads, desired, desired - 1))
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162 return false;
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163
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164 UpdateMaxThreads(desired);
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165
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166 return true;
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167 }
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168
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169 bool ReleaseThreadSlot(out bool last) {
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170 last = false;
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171 int current;
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172 // use spins to release slot for the new thread
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173 do {
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174 current = m_createdThreads;
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175 if (current <= m_minThreads && m_exitRequired == 0)
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176 // the thread is reserved
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177 return false;
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178 } while (current != Interlocked.CompareExchange(ref m_createdThreads, current - 1, current));
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179
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180 last = (current == 1);
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181
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182 return true;
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183 }
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184
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185 /// <summary>
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186 /// releases thread slot unconditionally, used during cleanup
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187 /// </summary>
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188 /// <returns>true - no more threads left</returns>
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189 bool ReleaseThreadSlotAnyway() {
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190 var left = Interlocked.Decrement(ref m_createdThreads);
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191 return left == 0;
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192 }
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193
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194 void UpdateMaxThreads(int count) {
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195 int max;
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196 do {
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197 max = m_maxRunningThreads;
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198 if (max >= count)
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199 break;
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200 } while(max != Interlocked.CompareExchange(ref m_maxRunningThreads, count, max));
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201 }
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202
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203 #endregion
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204
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205 bool StartWorker() {
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206 if (AllocateThreadSlot()) {
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207 // slot successfully allocated
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208 var worker = new Thread(this.Worker);
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209 worker.IsBackground = true;
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210 worker.Start();
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211
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212 return true;
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213 } else {
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214 return false;
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215 }
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216 }
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217
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218 bool FetchTask(out TUnit unit) {
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219 do {
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220 // exit if requested
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221 if (m_exitRequired != 0) {
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222 // release the thread slot
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223 Interlocked.Decrement(ref m_activeThreads);
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224 if (ReleaseThreadSlotAnyway()) // it was the last worker
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225 m_hasTasks.Dispose();
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226 else
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227 m_hasTasks.Set(); // wake next worker
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228 unit = default(TUnit);
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229 return false;
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230 }
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231
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232 // fetch task
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233 if (TryDequeue(out unit)) {
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234 ExtendPool();
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235 return true;
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236 }
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237
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238 Interlocked.Decrement(ref m_activeThreads);
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239
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240 // entering suspend state
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241 // keep this thread and wait
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242 if (!Suspend())
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243 return false;
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244
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245 Interlocked.Increment(ref m_activeThreads);
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246 } while (true);
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247 }
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248
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249 protected abstract void InvokeUnit(TUnit unit);
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250
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251 void Worker() {
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252 TUnit unit;
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253 Interlocked.Increment(ref m_activeThreads);
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254 while (FetchTask(out unit))
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255 InvokeUnit(unit);
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256 }
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257
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258 protected virtual void Dispose(bool disposing) {
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259 if (disposing) {
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260 if (m_exitRequired == 0) {
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261 if (Interlocked.CompareExchange(ref m_exitRequired, 1, 0) != 0)
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262 return;
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263
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264 // wake sleeping threads
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265 m_hasTasks.Set();
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266 GC.SuppressFinalize(this);
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267 }
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268 }
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269 }
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270
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271 public void Dispose() {
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272 Dispose(true);
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273 }
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274
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275 ~DispatchPool() {
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276 Dispose(false);
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277 }
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278 }
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279 }
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