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comparison Implab/Parallels/DispatchPool.cs @ 81:2c5631b43c7d v2

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dispatch pool rewritten
author cin
date Fri, 26 Sep 2014 20:44:01 +0400
parents 4f20870d0816
children ce0171cacec4
comparison
equal deleted inserted replaced
80:4f20870d0816 81:2c5631b43c7d
5 using System.Threading; 5 using System.Threading;
6 using System.Diagnostics; 6 using System.Diagnostics;
7 7
8 namespace Implab.Parallels { 8 namespace Implab.Parallels {
9 public abstract class DispatchPool<TUnit> : IDisposable { 9 public abstract class DispatchPool<TUnit> : IDisposable {
10 readonly int m_minThreads; 10 readonly int m_minThreadsLimit;
11 readonly int m_maxThreads; 11 readonly int m_maxThreadsLimit;
12 readonly int m_releaseTimeout = 100; // the timeout while the working thread will wait for the new tasks before exit 12 readonly int m_releaseTimeout = 1000; // the timeout while the working thread will wait for the new tasks before exit
13 13
14 int m_createdThreads = 0; // the current size of the pool 14 int m_threads = 0; // the current size of the pool
15 int m_activeThreads = 0; // the count of threads which are active
16 int m_sleepingThreads = 0; // the count of currently inactive threads
17 int m_maxRunningThreads = 0; // the meximum reached size of the pool 15 int m_maxRunningThreads = 0; // the meximum reached size of the pool
18 int m_exitRequired = 0; // the pool is going to shutdown, all unused workers are released 16 int m_exit = 0; // the pool is going to shutdown, all unused workers are released
19 17
20 int m_wakeEvents = 0; // the count of wake events 18 readonly object m_signal = new object(); // used to pulse waiting threads
21
22 readonly object m_signalLocker = new object();
23 19
24 protected DispatchPool(int min, int max) { 20 protected DispatchPool(int min, int max) {
25 if (min < 0) 21 if (min < 0)
26 throw new ArgumentOutOfRangeException("min"); 22 throw new ArgumentOutOfRangeException("min");
27 if (max <= 0) 23 if (max <= 0)
28 throw new ArgumentOutOfRangeException("max"); 24 throw new ArgumentOutOfRangeException("max");
29 25
30 if (min > max) 26 if (min > max)
31 min = max; 27 min = max;
32 m_minThreads = min; 28 m_minThreadsLimit = min;
33 m_maxThreads = max; 29 m_maxThreadsLimit = max;
34 } 30 }
35 31
36 protected DispatchPool(int threads) 32 protected DispatchPool(int threads)
37 : this(threads, threads) { 33 : this(threads, threads) {
38 } 34 }
39 35
40 protected DispatchPool() { 36 protected DispatchPool() {
41 int maxThreads, maxCP; 37 int maxThreads, maxCP;
42 ThreadPool.GetMaxThreads(out maxThreads, out maxCP); 38 ThreadPool.GetMaxThreads(out maxThreads, out maxCP);
43 39
44 m_minThreads = 0; 40 m_minThreadsLimit = 0;
45 m_maxThreads = maxThreads; 41 m_maxThreadsLimit = maxThreads;
46 } 42 }
47 43
48 protected void InitPool() { 44 protected void InitPool() {
49 for (int i = 0; i < m_minThreads; i++) 45 for (int i = 0; i < m_minThreadsLimit; i++)
50 StartWorker(); 46 StartWorker();
51 } 47 }
52 48
53 public int PoolSize { 49 public int PoolSize {
54 get { 50 get {
55 Thread.MemoryBarrier(); 51 Thread.MemoryBarrier();
56 return m_createdThreads; 52 return m_threads;
57 } 53 }
58 } 54 }
59 55
60 public int ActiveThreads {
61 get {
62 Thread.MemoryBarrier();
63 return m_activeThreads;
64 }
65 }
66
67 public int MaxRunningThreads { 56 public int MaxRunningThreads {
68 get { 57 get {
69 Thread.MemoryBarrier(); 58 Thread.MemoryBarrier();
70 return m_maxRunningThreads; 59 return m_maxRunningThreads;
71 } 60 }
72 } 61 }
73 62
74 protected bool IsDisposed { 63 protected bool IsDisposed {
75 get { 64 get {
76 Thread.MemoryBarrier(); 65 Thread.MemoryBarrier();
77 return m_exitRequired == 1; 66 return m_exit == 1;
78 } 67 }
79 } 68 }
80 69
81 protected abstract bool TryDequeue(out TUnit unit); 70 protected abstract bool TryDequeue(out TUnit unit);
82 71
83 #region thread signaling traits 72 private bool Dequeue(out TUnit unit, int timeout) {
84 int SignalThread() { 73 int ts = Environment.TickCount;
85 var signals = Interlocked.Increment(ref m_wakeEvents); 74 if (TryDequeue(out unit))
86 if(signals == 1) 75 return true;
87 lock(m_signalLocker) 76 lock (m_signal) {
88 Monitor.Pulse(m_signalLocker); 77 while (!TryDequeue(out unit) && m_exit == 0)
89 return signals; 78 if(!Monitor.Wait(m_signal, Math.Max(0, ts + timeout - Environment.TickCount))) {
90 } 79 // timeout
91 80 return false;
92 bool FetchSignalOrWait(int timeout) {
93 var start = Environment.TickCount;
94 int signals;
95 Thread.MemoryBarrier(); // m_wakeEvents volatile first read
96 do {
97 signals = m_wakeEvents;
98 if (signals == 0)
99 break;
100 } while (Interlocked.CompareExchange(ref m_wakeEvents, signals - 1, signals) != signals);
101
102 if (signals == 0) {
103 // no signal is fetched
104 lock(m_signalLocker) {
105 while(m_wakeEvents == 0) {
106 if (timeout != -1)
107 timeout = Math.Max(0, timeout - (Environment.TickCount - start));
108 if(!Monitor.Wait(m_signalLocker,timeout))
109 return false; // timeout
110 } 81 }
111 // m_wakeEvents > 0 82 // queue item or terminate
112 if (Interlocked.Decrement(ref m_wakeEvents) > 0) //syncronized 83 Monitor.Pulse(m_signal);
113 Monitor.Pulse(m_signalLocker); 84 if (m_exit == 1)
114 85 return false;
115 // signal fetched 86 }
116 return true; 87 return true;
117 } 88 }
118 89
119 } else { 90 protected void SignalThread() {
120 // signal fetched 91 lock (m_signal) {
121 return true; 92 Monitor.Pulse(m_signal);
122 } 93 }
123
124
125 }
126
127 bool Sleep(int timeout) {
128 Interlocked.Increment(ref m_sleepingThreads);
129 if (FetchSignalOrWait(timeout)) {
130 Interlocked.Decrement(ref m_sleepingThreads);
131 return true;
132 } else {
133 Interlocked.Decrement(ref m_sleepingThreads);
134 return false;
135 }
136 }
137 #endregion
138
139 /// <summary>
140 /// Запускает либо новый поток, если раньше не было ни одного потока, либо устанавливает событие пробуждение одного спящего потока
141 /// </summary>
142 protected void GrowPool() {
143 Thread.MemoryBarrier();
144 if (m_exitRequired == 1)
145 return;
146 if (m_sleepingThreads > m_wakeEvents) {
147 //Console.WriteLine("Waking threads (sleeps {0}, pending {1})", m_sleepingThreads, m_wakeEvents);
148
149 // all sleeping threads may gone
150 SignalThread(); // wake a sleeping thread;
151
152 // we can't check whether signal has been processed
153 // anyway it may take some time for the thread to start
154 // we will ensure that at least one thread is running
155
156 EnsurePoolIsAlive();
157 } else {
158 // if there is no sleeping threads in the pool
159 if (!StartWorker()) {
160 // we haven't started a new thread, but the current can be on the way to terminate and it can't process the queue
161 // send it a signal to spin again
162 SignalThread();
163 EnsurePoolIsAlive();
164 }
165 }
166 }
167
168 protected void EnsurePoolIsAlive() {
169 if (AllocateThreadSlot(1)) {
170 // if there were no threads in the pool
171 var worker = new Thread(this.Worker);
172 worker.IsBackground = true;
173 worker.Start();
174 }
175 }
176
177 protected virtual bool Suspend() {
178 //no tasks left, exit if the thread is no longer needed
179 bool last;
180 bool requestExit;
181
182 // if threads have a timeout before releasing
183 if (m_releaseTimeout > 0)
184 requestExit = !Sleep(m_releaseTimeout);
185 else
186 requestExit = true;
187
188 if (!requestExit)
189 return true;
190
191 // release unsused thread
192 if (requestExit && ReleaseThreadSlot(out last)) {
193 // in case at the moment the last thread was being released
194 // a new task was added to the queue, we need to try
195 // to revoke the thread to avoid the situation when the task is left unprocessed
196 if (last && FetchSignalOrWait(0)) { // FetchSignalOrWait(0) will fetch pending task or will return false
197 SignalThread(); // since FetchSignalOrWait(0) has fetched the signal we need to reschedule it
198 return AllocateThreadSlot(1); // ensure that at least one thread is alive
199 }
200
201 return false;
202 }
203
204 // wait till infinity
205 Sleep(-1);
206
207 return true;
208 } 94 }
209 95
210 #region thread slots traits 96 #region thread slots traits
211 97
212 bool AllocateThreadSlot() { 98 bool AllocateThreadSlot() {
213 int current; 99 int current;
214 // use spins to allocate slot for the new thread 100 // use spins to allocate slot for the new thread
215 do { 101 do {
216 current = m_createdThreads; 102 current = m_threads;
217 if (current >= m_maxThreads || m_exitRequired == 1) 103 if (current >= m_maxThreadsLimit || m_exit == 1)
218 // no more slots left or the pool has been disposed 104 // no more slots left or the pool has been disposed
219 return false; 105 return false;
220 } while (current != Interlocked.CompareExchange(ref m_createdThreads, current + 1, current)); 106 } while (current != Interlocked.CompareExchange(ref m_threads, current + 1, current));
221 107
222 UpdateMaxThreads(current + 1); 108 UpdateMaxThreads(current + 1);
223 109
224 return true; 110 return true;
225 } 111 }
226 112
227 bool AllocateThreadSlot(int desired) { 113 bool AllocateThreadSlot(int desired) {
228 if (desired - 1 != Interlocked.CompareExchange(ref m_createdThreads, desired, desired - 1)) 114 if (desired - 1 != Interlocked.CompareExchange(ref m_threads, desired, desired - 1))
229 return false; 115 return false;
230 116
231 UpdateMaxThreads(desired); 117 UpdateMaxThreads(desired);
232 118
233 return true; 119 return true;
237 last = false; 123 last = false;
238 int current; 124 int current;
239 // use spins to release slot for the new thread 125 // use spins to release slot for the new thread
240 Thread.MemoryBarrier(); 126 Thread.MemoryBarrier();
241 do { 127 do {
242 current = m_createdThreads; 128 current = m_threads;
243 if (current <= m_minThreads && m_exitRequired == 0) 129 if (current <= m_minThreadsLimit && m_exit == 0)
244 // the thread is reserved 130 // the thread is reserved
245 return false; 131 return false;
246 } while (current != Interlocked.CompareExchange(ref m_createdThreads, current - 1, current)); 132 } while (current != Interlocked.CompareExchange(ref m_threads, current - 1, current));
247 133
248 last = (current == 1); 134 last = (current == 1);
249 135
250 return true; 136 return true;
251 }
252
253 /// <summary>
254 /// releases thread slot unconditionally, used during cleanup
255 /// </summary>
256 /// <returns>true - no more threads left</returns>
257 bool ReleaseThreadSlotAnyway() {
258 var left = Interlocked.Decrement(ref m_createdThreads);
259 return left == 0;
260 } 137 }
261 138
262 void UpdateMaxThreads(int count) { 139 void UpdateMaxThreads(int count) {
263 int max; 140 int max;
264 do { 141 do {
268 } while(max != Interlocked.CompareExchange(ref m_maxRunningThreads, count, max)); 145 } while(max != Interlocked.CompareExchange(ref m_maxRunningThreads, count, max));
269 } 146 }
270 147
271 #endregion 148 #endregion
272 149
273 bool StartWorker() { 150 protected bool StartWorker() {
274 if (AllocateThreadSlot()) { 151 if (AllocateThreadSlot()) {
275 // slot successfully allocated 152 // slot successfully allocated
276 var worker = new Thread(this.Worker); 153 var worker = new Thread(this.Worker);
277 worker.IsBackground = true; 154 worker.IsBackground = true;
278 Interlocked.Increment(ref m_activeThreads);
279 worker.Start(); 155 worker.Start();
280 156
281 return true; 157 return true;
282 } else { 158 } else {
283 return false; 159 return false;
286 162
287 protected abstract void InvokeUnit(TUnit unit); 163 protected abstract void InvokeUnit(TUnit unit);
288 164
289 protected virtual void Worker() { 165 protected virtual void Worker() {
290 TUnit unit; 166 TUnit unit;
291 //Console.WriteLine("{0}: Active", Thread.CurrentThread.ManagedThreadId); 167 bool last;
292 int count = 0;; 168 do {
293 Thread.MemoryBarrier(); 169 while (Dequeue(out unit, m_releaseTimeout)) {
294 do { 170 InvokeUnit(unit);
295 // exit if requested
296 if (m_exitRequired == 1) {
297 // release the thread slot
298 Interlocked.Decrement(ref m_activeThreads);
299 if (!ReleaseThreadSlotAnyway()) // it was the last worker
300 SignalThread(); // wake next worker
301 break;
302 } 171 }
303 172 if(!ReleaseThreadSlot(out last))
304 // fetch task 173 continue;
305 if (TryDequeue(out unit)) { 174 // queue may be not empty
175 if (last && TryDequeue(out unit)) {
306 InvokeUnit(unit); 176 InvokeUnit(unit);
307 count ++; 177 if (AllocateThreadSlot(1))
308 continue; 178 continue;
179 // we can safely exit since pool is alive
309 } 180 }
310 Interlocked.Decrement(ref m_activeThreads); 181 break;
311 182 } while(true);
312 Console.WriteLine("{0}: Suspend processed({1})", Thread.CurrentThread.ManagedThreadId,count); 183 }
313 // entering suspend state 184
314 // keep this thread and wait
315 if (!Suspend())
316 break;
317 count = 0;
318 //Console.WriteLine("{0}: Awake", Thread.CurrentThread.ManagedThreadId);
319 Interlocked.Increment(ref m_activeThreads);
320 } while (true);
321 //Console.WriteLine("{0}: Exited", Thread.CurrentThread.ManagedThreadId);
322 }
323 185
324 protected virtual void Dispose(bool disposing) { 186 protected virtual void Dispose(bool disposing) {
325 if (disposing) { 187 if (disposing) {
326 if (0 == Interlocked.CompareExchange(ref m_exitRequired, 1, 0)) { // implies memory barrier 188 if (0 == Interlocked.CompareExchange(ref m_exit, 1, 0)) { // implies memory barrier
327 // wake sleeping threads 189 // wake sleeping threads
328 if (m_createdThreads > 0) 190 SignalThread();
329 SignalThread();
330 GC.SuppressFinalize(this); 191 GC.SuppressFinalize(this);
331 } 192 }
332 } 193 }
333 } 194 }
334 195