bundles/org.eclipse.core.jobs/src/org/eclipse/core/internal/jobs/WorkerPool.java - gerrit/platform/eclipse.platform.runtime - Git at Google

 /*******************************************************************************
  *  Copyright (c) 2003, 2012 IBM Corporation and others.
  *
  *  This program and the accompanying materials
  *  are made available under the terms of the Eclipse Public License 2.0
  *  which accompanies this distribution, and is available at
  *  https://www.eclipse.org/legal/epl-2.0/
  *
  *  SPDX-License-Identifier: EPL-2.0
  *
  *  Contributors:
  *     IBM - Initial API and implementation
  *     salesforce.com - limit number of sleeping worker threads
  *******************************************************************************/
 package org.eclipse.core.internal.jobs;

 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.jobs.Job;

 /**
  * Maintains a pool of worker threads. Threads are constructed lazily as
  * required, and are eventually discarded if not in use for awhile. This class
  * maintains the thread creation/destruction policies for the job manager.
  *
  * Implementation note: all the data structures of this class are protected
  * by the instance's object monitor.  To avoid deadlock with third party code,
  * this lock is never held when calling methods outside this class that may in
  * turn use locks.
  */
 class WorkerPool {
 	/**
 	 * Threads not used by their best before timestamp are destroyed.
 	 */
 	private static final int BEST_BEFORE = 60000;
 	/**
 	 * There will always be at least MIN_THREADS workers in the pool.
 	 */
 	private static final int MIN_THREADS = 1;

 	/**
 	 * Soft limit on the maximum number of workers in the pool. An idle worker
 	 * is not put back in the pool if the total number of workers is more than
 	 * MAX_THREADS.
 	 */
 	private static final int MAX_THREADS = 50;

 	/**
 	 * Use the busy thread count to avoid starting new threads when a living
 	 * thread is just doing house cleaning (notifying listeners, etc).
 	 */
 	private int busyThreads = 0;

 	/**
 	 * The default context class loader to use when creating worker threads.
 	 */
 	protected final ClassLoader defaultContextLoader;

 	/**
 	 * Records whether new worker threads should be daemon threads.
 	 */
 	private boolean isDaemon = false;

 	private JobManager manager;
 	/**
 	 * The number of workers in the threads array
 	 */
 	private int numThreads = 0;
 	/**
 	 * The number of threads that are currently sleeping
 	 */
 	private int sleepingThreads = 0;
 	/**
 	 * The living set of workers in this pool.
 	 */
 	private Worker[] threads = new Worker[10];

 	protected WorkerPool(JobManager manager) {
 		this.manager = manager;
 		this.defaultContextLoader = Thread.currentThread().getContextClassLoader();
 	}

 	/**
 	 * Adds a worker to the list of workers.
 	 */
 	private synchronized void add(Worker worker) {
 		int size = threads.length;
 		if (numThreads + 1 > size) {
 			Worker[] newThreads = new Worker[2 * size];
 			System.arraycopy(threads, 0, newThreads, 0, size);
 			threads = newThreads;
 		}
 		threads[numThreads++] = worker;
 	}

 	private synchronized void decrementBusyThreads() {
 		//impossible to have less than zero busy threads
 		if (--busyThreads < 0) {
 			if (JobManager.DEBUG)
 				Assert.isTrue(false, Integer.toString(busyThreads));
 			busyThreads = 0;
 		}
 	}

 	/**
 	 * Signals the end of a job.  Note that this method can be called under
 	 * OutOfMemoryError conditions and thus must be paranoid about allocating objects.
 	 */
 	protected void endJob(InternalJob job, IStatus result) {
 		try {
 			//need to end rule in graph before ending job so that 2 threads
 			//do not become the owners of the same rule in the graph
 			if ((job.getRule() != null) && !(job instanceof ThreadJob)) {
 				//remove any locks this thread may be owning on that rule
 				manager.getLockManager().removeLockCompletely(Thread.currentThread(), job.getRule());
 			}
 			manager.endJob(job, result, true);
 			//ensure this thread no longer owns any scheduling rules
 			manager.implicitJobs.endJob(job);
 		} finally {
 			decrementBusyThreads();
 		}
 	}

 	/**
 	 * Signals the death of a worker thread.  Note that this method can be called under
 	 * OutOfMemoryError conditions and thus must be paranoid about allocating objects.
 	 */
 	protected synchronized void endWorker(Worker worker) {
 		if (remove(worker) && JobManager.DEBUG)
 			JobManager.debug("worker removed from pool: " + worker); //$NON-NLS-1$
 	}

 	private synchronized void incrementBusyThreads() {
 		//impossible to have more busy threads than there are threads
 		if (++busyThreads > numThreads) {
 			if (JobManager.DEBUG)
 				Assert.isTrue(false, Integer.toString(busyThreads) + ',' + numThreads);
 			busyThreads = numThreads;
 		}
 	}

 	/**
 	 * Notification that a job has been added to the queue. Wake a worker,
 	 * creating a new worker if necessary. The provided job may be null.
 	 */
 	protected synchronized void jobQueued() {
 		//if there is a sleeping thread, wake it up
 		if (sleepingThreads > 0) {
 			notify();
 			return;
 		}
 		//create a thread if all threads are busy
 		if (busyThreads >= numThreads) {
 			Worker worker = new Worker(this);
 			worker.setDaemon(isDaemon);
 			add(worker);
 			if (JobManager.DEBUG)
 				JobManager.debug("worker added to pool: " + worker); //$NON-NLS-1$
 			worker.start();
 			return;
 		}
 	}

 	/**
 	 * Remove a worker thread from our list.
 	 * @return true if a worker was removed, and false otherwise.
 	 */
 	private synchronized boolean remove(Worker worker) {
 		for (int i = 0; i < threads.length; i++) {
 			if (threads[i] == worker) {
 				System.arraycopy(threads, i + 1, threads, i, numThreads - i - 1);
 				threads[--numThreads] = null;
 				return true;
 			}
 		}
 		return false;
 	}

 	/**
 	 * Sets whether threads created in the worker pool should be daemon threads.
 	 */
 	void setDaemon(boolean value) {
 		this.isDaemon = value;
 	}

 	protected synchronized void shutdown() {
 		notifyAll();
 	}

 	/**
 	 * Sleep for the given duration or until woken.
 	 */
 	private synchronized void sleep(long duration) {
 		sleepingThreads++;
 		busyThreads--;
 		if (JobManager.DEBUG)
 			JobManager.debug("worker sleeping for: " + duration + "ms"); //$NON-NLS-1$ //$NON-NLS-2$
 		try {
 			wait(duration);
 		} catch (InterruptedException e) {
 			if (JobManager.DEBUG)
 				JobManager.debug("worker interrupted while waiting... :-|"); //$NON-NLS-1$
 		} finally {
 			sleepingThreads--;
 			busyThreads++;
 		}
 	}

 	/**
 	 * Returns a new job to run. Returns null if the thread should die.
 	 */
 	protected InternalJob startJob(Worker worker) {
 		// must endWorker and decrementBusyThreads from the same synchronized block
 		boolean busy;
 		synchronized (this) {
 			if (!manager.isActive()) {
 				//must remove the worker immediately to prevent all threads from expiring
 				endWorker(worker);
 				return null;
 			}
 			// set the thread to be busy now in case of reentrant scheduling
 			incrementBusyThreads();
 			busy = true;
 		}
 		Job job = null;
 		try {
 			job = manager.startJob(worker);
 			//spin until a job is found or until we have been idle for too long
 			long idleStart = manager.now();
 			while (manager.isActive() && job == null) {
 				long hint = manager.sleepHint();
 				if (hint > 0) {
 					synchronized (this) {
 						if (numThreads > MAX_THREADS) {
 							endWorker(worker);
 							decrementBusyThreads();
 							busy = false;
 							return null;
 						}
 					}
 					sleep(Math.min(hint, BEST_BEFORE));
 				}
 				job = manager.startJob(worker);
 				//if we were already idle, and there are still no new jobs, then
 				// the thread can expire
 				synchronized (this) {
 					if (job == null && (manager.now() - idleStart > BEST_BEFORE) && (numThreads - busyThreads) > MIN_THREADS) {
 						//must remove the worker immediately to prevent all threads from expiring
 						endWorker(worker);
 						decrementBusyThreads();
 						busy = false;
 						return null;
 					}
 				}
 				//if we didn't sleep but there was no job available, make sure we sleep to avoid a tight loop (bug 260724)
 				if (hint <= 0 && job == null)
 					sleep(50);
 			}
 			if (job != null) {
 				//if this job has a rule, then we are essentially acquiring a lock
 				if ((job.getRule() != null) && !(job instanceof ThreadJob)) {
 					//don't need to re-acquire locks because it was not recorded in the graph
 					//that this thread waited to get this rule
 					manager.getLockManager().addLockThread(Thread.currentThread(), job.getRule());
 				}
 				//see if we need to wake another worker
 				if (manager.sleepHint() < InternalJob.T_INFINITE)
 					jobQueued();
 			}
 		} finally {
 			//decrement busy thread count if we're not running a job
 			if (job == null && busy)
 				decrementBusyThreads();
 		}
 		return job;
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2003, 2012 IBM Corporation and others.
	*
	* This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License 2.0
	* which accompanies this distribution, and is available at
	* https://www.eclipse.org/legal/epl-2.0/
	*
	* SPDX-License-Identifier: EPL-2.0
	*
	* Contributors:
	* IBM - Initial API and implementation
	* salesforce.com - limit number of sleeping worker threads
	*******************************************************************************/
	package org.eclipse.core.internal.jobs;

	import org.eclipse.core.runtime.Assert;
	import org.eclipse.core.runtime.IStatus;
	import org.eclipse.core.runtime.jobs.Job;

	/**
	* Maintains a pool of worker threads. Threads are constructed lazily as
	* required, and are eventually discarded if not in use for awhile. This class
	* maintains the thread creation/destruction policies for the job manager.
	*
	* Implementation note: all the data structures of this class are protected
	* by the instance's object monitor. To avoid deadlock with third party code,
	* this lock is never held when calling methods outside this class that may in
	* turn use locks.
	*/
	class WorkerPool {
	/**
	* Threads not used by their best before timestamp are destroyed.
	*/
	private static final int BEST_BEFORE = 60000;
	/**
	* There will always be at least MIN_THREADS workers in the pool.
	*/
	private static final int MIN_THREADS = 1;

	/**
	* Soft limit on the maximum number of workers in the pool. An idle worker
	* is not put back in the pool if the total number of workers is more than
	* MAX_THREADS.
	*/
	private static final int MAX_THREADS = 50;

	/**
	* Use the busy thread count to avoid starting new threads when a living
	* thread is just doing house cleaning (notifying listeners, etc).
	*/
	private int busyThreads = 0;

	/**
	* The default context class loader to use when creating worker threads.
	*/
	protected final ClassLoader defaultContextLoader;

	/**
	* Records whether new worker threads should be daemon threads.
	*/
	private boolean isDaemon = false;

	private JobManager manager;
	/**
	* The number of workers in the threads array
	*/
	private int numThreads = 0;
	/**
	* The number of threads that are currently sleeping
	*/
	private int sleepingThreads = 0;
	/**
	* The living set of workers in this pool.
	*/
	private Worker[] threads = new Worker[10];

	protected WorkerPool(JobManager manager) {
	this.manager = manager;
	this.defaultContextLoader = Thread.currentThread().getContextClassLoader();
	}

	/**
	* Adds a worker to the list of workers.
	*/
	private synchronized void add(Worker worker) {
	int size = threads.length;
	if (numThreads + 1 > size) {
	Worker[] newThreads = new Worker[2 * size];
	System.arraycopy(threads, 0, newThreads, 0, size);
	threads = newThreads;
	}
	threads[numThreads++] = worker;
	}

	private synchronized void decrementBusyThreads() {
	//impossible to have less than zero busy threads
	if (--busyThreads < 0) {
	if (JobManager.DEBUG)
	Assert.isTrue(false, Integer.toString(busyThreads));
	busyThreads = 0;
	}
	}

	/**
	* Signals the end of a job. Note that this method can be called under
	* OutOfMemoryError conditions and thus must be paranoid about allocating objects.
	*/
	protected void endJob(InternalJob job, IStatus result) {
	try {
	//need to end rule in graph before ending job so that 2 threads
	//do not become the owners of the same rule in the graph
	if ((job.getRule() != null) && !(job instanceof ThreadJob)) {
	//remove any locks this thread may be owning on that rule
	manager.getLockManager().removeLockCompletely(Thread.currentThread(), job.getRule());
	}
	manager.endJob(job, result, true);
	//ensure this thread no longer owns any scheduling rules
	manager.implicitJobs.endJob(job);
	} finally {
	decrementBusyThreads();
	}
	}

	/**
	* Signals the death of a worker thread. Note that this method can be called under
	* OutOfMemoryError conditions and thus must be paranoid about allocating objects.
	*/
	protected synchronized void endWorker(Worker worker) {
	if (remove(worker) && JobManager.DEBUG)
	JobManager.debug("worker removed from pool: " + worker); //$NON-NLS-1$
	}

	private synchronized void incrementBusyThreads() {
	//impossible to have more busy threads than there are threads
	if (++busyThreads > numThreads) {
	if (JobManager.DEBUG)
	Assert.isTrue(false, Integer.toString(busyThreads) + ',' + numThreads);
	busyThreads = numThreads;
	}
	}

	/**
	* Notification that a job has been added to the queue. Wake a worker,
	* creating a new worker if necessary. The provided job may be null.
	*/
	protected synchronized void jobQueued() {
	//if there is a sleeping thread, wake it up
	if (sleepingThreads > 0) {
	notify();
	return;
	}
	//create a thread if all threads are busy
	if (busyThreads >= numThreads) {
	Worker worker = new Worker(this);
	worker.setDaemon(isDaemon);
	add(worker);
	if (JobManager.DEBUG)
	JobManager.debug("worker added to pool: " + worker); //$NON-NLS-1$
	worker.start();
	return;
	}
	}

	/**
	* Remove a worker thread from our list.
	* @return true if a worker was removed, and false otherwise.
	*/
	private synchronized boolean remove(Worker worker) {
	for (int i = 0; i < threads.length; i++) {
	if (threads[i] == worker) {
	System.arraycopy(threads, i + 1, threads, i, numThreads - i - 1);
	threads[--numThreads] = null;
	return true;
	}
	}
	return false;
	}

	/**
	* Sets whether threads created in the worker pool should be daemon threads.
	*/
	void setDaemon(boolean value) {
	this.isDaemon = value;
	}

	protected synchronized void shutdown() {
	notifyAll();
	}

	/**
	* Sleep for the given duration or until woken.
	*/
	private synchronized void sleep(long duration) {
	sleepingThreads++;
	busyThreads--;
	if (JobManager.DEBUG)
	JobManager.debug("worker sleeping for: " + duration + "ms"); //$NON-NLS-1$ //$NON-NLS-2$
	try {
	wait(duration);
	} catch (InterruptedException e) {
	if (JobManager.DEBUG)
	JobManager.debug("worker interrupted while waiting... :-\|"); //$NON-NLS-1$
	} finally {
	sleepingThreads--;
	busyThreads++;
	}
	}

	/**
	* Returns a new job to run. Returns null if the thread should die.
	*/
	protected InternalJob startJob(Worker worker) {
	// must endWorker and decrementBusyThreads from the same synchronized block
	boolean busy;
	synchronized (this) {
	if (!manager.isActive()) {
	//must remove the worker immediately to prevent all threads from expiring
	endWorker(worker);
	return null;
	}
	// set the thread to be busy now in case of reentrant scheduling
	incrementBusyThreads();
	busy = true;
	}
	Job job = null;
	try {
	job = manager.startJob(worker);
	//spin until a job is found or until we have been idle for too long
	long idleStart = manager.now();
	while (manager.isActive() && job == null) {
	long hint = manager.sleepHint();
	if (hint > 0) {
	synchronized (this) {
	if (numThreads > MAX_THREADS) {
	endWorker(worker);
	decrementBusyThreads();
	busy = false;
	return null;
	}
	}
	sleep(Math.min(hint, BEST_BEFORE));
	}
	job = manager.startJob(worker);
	//if we were already idle, and there are still no new jobs, then
	// the thread can expire
	synchronized (this) {
	if (job == null && (manager.now() - idleStart > BEST_BEFORE) && (numThreads - busyThreads) > MIN_THREADS) {
	//must remove the worker immediately to prevent all threads from expiring
	endWorker(worker);
	decrementBusyThreads();
	busy = false;
	return null;
	}
	}
	//if we didn't sleep but there was no job available, make sure we sleep to avoid a tight loop (bug 260724)
	if (hint <= 0 && job == null)
	sleep(50);
	}
	if (job != null) {
	//if this job has a rule, then we are essentially acquiring a lock
	if ((job.getRule() != null) && !(job instanceof ThreadJob)) {
	//don't need to re-acquire locks because it was not recorded in the graph
	//that this thread waited to get this rule
	manager.getLockManager().addLockThread(Thread.currentThread(), job.getRule());
	}
	//see if we need to wake another worker
	if (manager.sleepHint() < InternalJob.T_INFINITE)
	jobQueued();
	}
	} finally {
	//decrement busy thread count if we're not running a job
	if (job == null && busy)
	decrementBusyThreads();
	}
	return job;
	}
	}