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comparison dwtx/core/internal/jobs/WorkerPool.d @ 122:9d0585bcb7aa

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Add core.jobs package
author Frank Benoit <benoit@tionex.de>
date Tue, 12 Aug 2008 02:34:21 +0200
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121:c0304616ea23 122:9d0585bcb7aa
1 /*******************************************************************************
2 * Copyright (c) 2003, 2007 IBM Corporation and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * IBM - Initial API and implementation
10 * Port to the D programming language:
11 * Frank Benoit <benoit@tionex.de>
12 *******************************************************************************/
13 module dwtx.core.internal.jobs.WorkerPool;
14
15 import tango.core.Thread;
16 import tango.core.sync.Mutex;
17 import tango.core.sync.Condition;
18 import tango.text.convert.Format;
19 import dwt.dwthelper.utils;
20
21 import dwtx.core.runtime.Assert;
22 import dwtx.core.runtime.IStatus;
23 import dwtx.core.runtime.jobs.Job;
24 import dwtx.core.internal.jobs.JobManager;
25 import dwtx.core.internal.jobs.Worker;
26
27 import dwtx.core.internal.jobs.InternalJob;
28 import dwtx.core.internal.jobs.ThreadJob;
29
30 /**
31 * Maintains a pool of worker threads. Threads are constructed lazily as
32 * required, and are eventually discarded if not in use for awhile. This class
33 * maintains the thread creation/destruction policies for the job manager.
34 *
35 * Implementation note: all the data structures of this class are protected
36 * by the instance's object monitor. To avoid deadlock with third party code,
37 * this lock is never held when calling methods outside this class that may in
38 * turn use locks.
39 */
40 class WorkerPool {
41
42 protected Mutex mutex;
43 protected Condition condition;
44
45
46 /**
47 * Threads not used by their best before timestamp are destroyed.
48 */
49 private static const int BEST_BEFORE = 60000;
50 /**
51 * There will always be at least MIN_THREADS workers in the pool.
52 */
53 private static const int MIN_THREADS = 1;
54 /**
55 * Use the busy thread count to avoid starting new threads when a living
56 * thread is just doing house cleaning (notifying listeners, etc).
57 */
58 private int busyThreads = 0;
59
60 /**
61 * The default context class loader to use when creating worker threads.
62 */
63 // protected const ClassLoader defaultContextLoader;
64
65 /**
66 * Records whether new worker threads should be daemon threads.
67 */
68 private bool isDaemon = false;
69
70 private JobManager manager;
71 /**
72 * The number of workers in the threads array
73 */
74 private int numThreads = 0;
75 /**
76 * The number of threads that are currently sleeping
77 */
78 private int sleepingThreads = 0;
79 /**
80 * The living set of workers in this pool.
81 */
82 private Worker[] threads;
83
84 protected package this(JobManager manager) {
85 threads = new Worker[10];
86 this.manager = manager;
87 mutex = new Mutex;
88 condition = new Condition(mutex);
89 // this.defaultContextLoader = Thread.currentThread().getContextClassLoader();
90 }
91
92 /**
93 * Adds a worker to the list of workers.
94 */
95 private void add(Worker worker) {
96 synchronized(mutex){
97 int size = threads.length;
98 if (numThreads + 1 > size) {
99 Worker[] newThreads = new Worker[2 * size];
100 System.arraycopy(threads, 0, newThreads, 0, size);
101 threads = newThreads;
102 }
103 threads[numThreads++] = worker;
104 }
105 }
106
107 private void decrementBusyThreads() {
108 synchronized(mutex){
109 //impossible to have less than zero busy threads
110 if (--busyThreads < 0) {
111 if (JobManager.DEBUG)
112 Assert.isTrue(false, Integer.toString(busyThreads));
113 busyThreads = 0;
114 }
115 }
116 }
117
118 /**
119 * Signals the end of a job. Note that this method can be called under
120 * OutOfMemoryError conditions and thus must be paranoid about allocating objects.
121 */
122 protected void endJob(InternalJob job, IStatus result) {
123 decrementBusyThreads();
124 //need to end rule in graph before ending job so that 2 threads
125 //do not become the owners of the same rule in the graph
126 if ((job.getRule_package() !is null) && !(cast(ThreadJob)job )) {
127 //remove any locks this thread may be owning on that rule
128 manager.getLockManager().removeLockCompletely(Thread.getThis(), job.getRule_package());
129 }
130 manager.endJob_package(job, result, true);
131 //ensure this thread no longer owns any scheduling rules
132 manager.implicitJobs.endJob(job);
133 }
134 package void endJob_package(InternalJob job, IStatus result) {
135 endJob(job, result);
136 }
137
138 /**
139 * Signals the death of a worker thread. Note that this method can be called under
140 * OutOfMemoryError conditions and thus must be paranoid about allocating objects.
141 */
142 protected void endWorker(Worker worker) {
143 synchronized(mutex){
144 if (remove(worker) && JobManager.DEBUG)
145 JobManager.debug_(Format("worker removed from pool: {}", worker)); //$NON-NLS-1$
146 }
147 }
148 package void endWorker_package(Worker worker) {
149 endWorker(worker);
150 }
151
152 private void incrementBusyThreads() {
153 synchronized(mutex){
154 //impossible to have more busy threads than there are threads
155 if (++busyThreads > numThreads) {
156 if (JobManager.DEBUG)
157 Assert.isTrue(false, Format( "{},{}", busyThreads, numThreads));
158 busyThreads = numThreads;
159 }
160 }
161 }
162
163 /**
164 * Notification that a job has been added to the queue. Wake a worker,
165 * creating a new worker if necessary. The provided job may be null.
166 */
167 protected package void jobQueued() {
168 synchronized(mutex){
169 //if there is a sleeping thread, wake it up
170 if (sleepingThreads > 0) {
171 condition.notify();
172 return;
173 }
174 //create a thread if all threads are busy
175 if (busyThreads >= numThreads) {
176 Worker worker = new Worker(this);
177 worker.isDaemon(isDaemon);
178 add(worker);
179 if (JobManager.DEBUG)
180 JobManager.debug_(Format("worker added to pool: {}", worker)); //$NON-NLS-1$
181 worker.start();
182 return;
183 }
184 }
185 }
186
187 /**
188 * Remove a worker thread from our list.
189 * @return true if a worker was removed, and false otherwise.
190 */
191 private bool remove(Worker worker) {
192 synchronized(mutex){
193 for (int i = 0; i < threads.length; i++) {
194 if (threads[i] is worker) {
195 System.arraycopy(threads, i + 1, threads, i, numThreads - i - 1);
196 threads[--numThreads] = null;
197 return true;
198 }
199 }
200 return false;
201 }
202 }
203
204 /**
205 * Sets whether threads created in the worker pool should be daemon threads.
206 */
207 void setDaemon(bool value) {
208 this.isDaemon = value;
209 }
210
211 protected void shutdown() {
212 synchronized(mutex){
213 condition.notifyAll();
214 }
215 }
216 package void shutdown_package() {
217 shutdown();
218 }
219
220 /**
221 * Sleep for the given duration or until woken.
222 */
223 private void sleep(long duration) {
224 synchronized(mutex){
225 sleepingThreads++;
226 busyThreads--;
227 if (JobManager.DEBUG)
228 JobManager.debug_(Format("worker sleeping for: {}ms", duration)); //$NON-NLS-1$ //$NON-NLS-2$
229 try {
230 condition.wait(duration/1000.0f);
231 } catch (InterruptedException e) {
232 if (JobManager.DEBUG)
233 JobManager.debug_("worker interrupted while waiting... :-|"); //$NON-NLS-1$
234 } finally {
235 sleepingThreads--;
236 busyThreads++;
237 }
238 }
239 }
240
241 /**
242 * Returns a new job to run. Returns null if the thread should die.
243 */
244 protected InternalJob startJob(Worker worker) {
245 //if we're above capacity, kill the thread
246 synchronized (mutex) {
247 if (!manager.isActive_package()) {
248 //must remove the worker immediately to prevent all threads from expiring
249 endWorker(worker);
250 return null;
251 }
252 //set the thread to be busy now in case of reentrant scheduling
253 incrementBusyThreads();
254 }
255 Job job = null;
256 try {
257 job = manager.startJob_package();
258 //spin until a job is found or until we have been idle for too long
259 long idleStart = System.currentTimeMillis();
260 while (manager.isActive_package() && job is null) {
261 long hint = manager.sleepHint_package();
262 if (hint > 0)
263 sleep(Math.min(hint, BEST_BEFORE));
264 job = manager.startJob_package();
265 //if we were already idle, and there are still no new jobs, then
266 // the thread can expire
267 synchronized (mutex) {
268 if (job is null && (System.currentTimeMillis() - idleStart > BEST_BEFORE) && (numThreads - busyThreads) > MIN_THREADS) {
269 //must remove the worker immediately to prevent all threads from expiring
270 endWorker(worker);
271 return null;
272 }
273 }
274 }
275 if (job !is null) {
276 //if this job has a rule, then we are essentially acquiring a lock
277 if ((job.getRule() !is null) && !(cast(ThreadJob)job )) {
278 //don't need to re-aquire locks because it was not recorded in the graph
279 //that this thread waited to get this rule
280 manager.getLockManager().addLockThread(Thread.getThis(), job.getRule());
281 }
282 //see if we need to wake another worker
283 if (manager.sleepHint_package() <= 0)
284 jobQueued();
285 }
286 } finally {
287 //decrement busy thread count if we're not running a job
288 if (job is null)
289 decrementBusyThreads();
290 }
291 return job;
292 }
293 package InternalJob startJob_package(Worker worker) {
294 return startJob(worker);
295 }
296 }