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提交 d9898853 编写于 作者: M martin
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6602600: Fast removal of cancelled scheduled thread pool tasks 

Reviewed-by: alanb
Contributed-by: NDoug Lea <dl@cs.oswego.edu>
上级 37541d41
隐藏空白更改
内联 并排
Showing with 683 addition and 48 deletion
src/share/classes/java/util/concurrent/ScheduledThreadPoolExecutor.java
浏览文件 @ d9898853
......@@ -35,6 +35,7 @@
package java.util.concurrent;
import java.util.concurrent.atomic.*;
import java.util.concurrent.locks.*;
import java.util.*;
/**
......@@ -45,12 +46,21 @@ import java.util.*;
* flexibility or capabilities of {@link ThreadPoolExecutor} (which
* this class extends) are required.
*
* <p> Delayed tasks execute no sooner than they are enabled, but
* <p>Delayed tasks execute no sooner than they are enabled, but
* without any real-time guarantees about when, after they are
* enabled, they will commence. Tasks scheduled for exactly the same
* execution time are enabled in first-in-first-out (FIFO) order of
* submission.
*
* <p>When a submitted task is cancelled before it is run, execution
* is suppressed. By default, such a cancelled task is not
* automatically removed from the work queue until its delay
* elapses. While this enables further inspection and monitoring, it
* may also cause unbounded retention of cancelled tasks. To avoid
* this, set {@link #setRemoveOnCancelPolicy} to {@code true}, which
* causes tasks to be immediately removed from the work queue at
* time of cancellation.
*
* <p>While this class inherits from {@link ThreadPoolExecutor}, a few
* of the inherited tuning methods are not useful for it. In
* particular, because it acts as a fixed-sized pool using
......@@ -111,21 +121,11 @@ public class ScheduledThreadPoolExecutor
* ScheduledExecutorService methods) which are treated as
* delayed tasks with a delay of zero.
*
* 2. Using a custom queue (DelayedWorkQueue) based on an
* 2. Using a custom queue (DelayedWorkQueue), a variant of
* unbounded DelayQueue. The lack of capacity constraint and
* the fact that corePoolSize and maximumPoolSize are
* effectively identical simplifies some execution mechanics
* (see delayedExecute) compared to ThreadPoolExecutor
* version.
*
* The DelayedWorkQueue class is defined below for the sake of
* ensuring that all elements are instances of
* RunnableScheduledFuture. Since DelayQueue otherwise
* requires type be Delayed, but not necessarily Runnable, and
* the workQueue requires the opposite, we need to explicitly
* define a class that requires both to ensure that users don't
* add objects that aren't RunnableScheduledFutures via
* getQueue().add() etc.
* (see delayedExecute) compared to ThreadPoolExecutor.
*
* 3. Supporting optional run-after-shutdown parameters, which
* leads to overrides of shutdown methods to remove and cancel
......@@ -149,6 +149,11 @@ public class ScheduledThreadPoolExecutor
*/
private volatile boolean executeExistingDelayedTasksAfterShutdown = true;
/**
* True if ScheduledFutureTask.cancel should remove from queue
*/
private volatile boolean removeOnCancel = false;
/**
* Sequence number to break scheduling ties, and in turn to
* guarantee FIFO order among tied entries.
......@@ -167,8 +172,10 @@ public class ScheduledThreadPoolExecutor
/** Sequence number to break ties FIFO */
private final long sequenceNumber;
/** The time the task is enabled to execute in nanoTime units */
private long time;
/**
* Period in nanoseconds for repeating tasks. A positive
* value indicates fixed-rate execution. A negative value
......@@ -180,6 +187,11 @@ public class ScheduledThreadPoolExecutor
/** The actual task to be re-enqueued by reExecutePeriodic */
RunnableScheduledFuture<V> outerTask = this;
/**
* Index into delay queue, to support faster cancellation.
*/
int heapIndex;
/**
* Creates a one-shot action with given nanoTime-based trigger time.
*/
......@@ -255,6 +267,13 @@ public class ScheduledThreadPoolExecutor
time = now() - p;
}
public boolean cancel(boolean mayInterruptIfRunning) {
boolean cancelled = super.cancel(mayInterruptIfRunning);
if (cancelled && removeOnCancel && heapIndex >= 0)
remove(this);
return cancelled;
}
/**
* Overrides FutureTask version so as to reset/requeue if periodic.
*/
......@@ -654,6 +673,33 @@ public class ScheduledThreadPoolExecutor
return executeExistingDelayedTasksAfterShutdown;
}
/**
* Sets the policy on whether cancelled tasks should be immediately
* removed from the work queue at time of cancellation. This value is
* by default {@code false}.
*
* @param value if {@code true}, remove on cancellation, else don't
* @see #getRemoveOnCancelPolicy
* @since 1.7
*/
public void setRemoveOnCancelPolicy(boolean value) {
removeOnCancel = value;
}
/**
* Gets the policy on whether cancelled tasks should be immediately
* removed from the work queue at time of cancellation. This value is
* by default {@code false}.
*
* @return {@code true} if cancelled tasks are immediately removed
* from the queue
* @see #setRemoveOnCancelPolicy
* @since 1.7
*/
public boolean getRemoveOnCancelPolicy() {
return removeOnCancel;
}
/**
* Initiates an orderly shutdown in which previously submitted
* tasks are executed, but no new tasks will be accepted. If the
......@@ -707,56 +753,478 @@ public class ScheduledThreadPoolExecutor
}
/**
* An annoying wrapper class to convince javac to use a
* DelayQueue<RunnableScheduledFuture> as a BlockingQueue<Runnable>
* Specialized delay queue. To mesh with TPE declarations, this
* class must be declared as a BlockingQueue<Runnable> even though
* it can only hold RunnableScheduledFutures.
*/
private static class DelayedWorkQueue
extends AbstractCollection<Runnable>
static class DelayedWorkQueue extends AbstractQueue<Runnable>
implements BlockingQueue<Runnable> {
private final DelayQueue<RunnableScheduledFuture> dq = new DelayQueue<RunnableScheduledFuture>();
public Runnable poll() { return dq.poll(); }
public Runnable peek() { return dq.peek(); }
public Runnable take() throws InterruptedException { return dq.take(); }
public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException {
return dq.poll(timeout, unit);
/*
* A DelayedWorkQueue is based on a heap-based data structure
* like those in DelayQueue and PriorityQueue, except that
* every ScheduledFutureTask also records its index into the
* heap array. This eliminates the need to find a task upon
* cancellation, greatly speeding up removal (down from O(n)
* to O(log n)), and reducing garbage retention that would
* otherwise occur by waiting for the element to rise to top
* before clearing. But because the queue may also hold
* RunnableScheduledFutures that are not ScheduledFutureTasks,
* we are not guaranteed to have such indices available, in
* which case we fall back to linear search. (We expect that
* most tasks will not be decorated, and that the faster cases
* will be much more common.)
*
* All heap operations must record index changes -- mainly
* within siftUp and siftDown. Upon removal, a task's
* heapIndex is set to -1. Note that ScheduledFutureTasks can
* appear at most once in the queue (this need not be true for
* other kinds of tasks or work queues), so are uniquely
* identified by heapIndex.
*/
private static final int INITIAL_CAPACITY = 16;
private RunnableScheduledFuture[] queue =
new RunnableScheduledFuture[INITIAL_CAPACITY];
private final ReentrantLock lock = new ReentrantLock();
private int size = 0;
/**
* Thread designated to wait for the task at the head of the
* queue. This variant of the Leader-Follower pattern
* (http://www.cs.wustl.edu/~schmidt/POSA/POSA2/) serves to
* minimize unnecessary timed waiting. When a thread becomes
* the leader, it waits only for the next delay to elapse, but
* other threads await indefinitely. The leader thread must
* signal some other thread before returning from take() or
* poll(...), unless some other thread becomes leader in the
* interim. Whenever the head of the queue is replaced with a
* task with an earlier expiration time, the leader field is
* invalidated by being reset to null, and some waiting
* thread, but not necessarily the current leader, is
* signalled. So waiting threads must be prepared to acquire
* and lose leadership while waiting.
*/
private Thread leader = null;
/**
* Condition signalled when a newer task becomes available at the
* head of the queue or a new thread may need to become leader.
*/
private final Condition available = lock.newCondition();
/**
* Set f's heapIndex if it is a ScheduledFutureTask.
*/
private void setIndex(RunnableScheduledFuture f, int idx) {
if (f instanceof ScheduledFutureTask)
((ScheduledFutureTask)f).heapIndex = idx;
}
/**
* Sift element added at bottom up to its heap-ordered spot.
* Call only when holding lock.
*/
private void siftUp(int k, RunnableScheduledFuture key) {
while (k > 0) {
int parent = (k - 1) >>> 1;
RunnableScheduledFuture e = queue[parent];
if (key.compareTo(e) >= 0)
break;
queue[k] = e;
setIndex(e, k);
k = parent;
}
queue[k] = key;
setIndex(key, k);
}
/**
* Sift element added at top down to its heap-ordered spot.
* Call only when holding lock.
*/
private void siftDown(int k, RunnableScheduledFuture key) {
int half = size >>> 1;
while (k < half) {
int child = (k << 1) + 1;
RunnableScheduledFuture c = queue[child];
int right = child + 1;
if (right < size && c.compareTo(queue[right]) > 0)
c = queue[child = right];
if (key.compareTo(c) <= 0)
break;
queue[k] = c;
setIndex(c, k);
k = child;
}
queue[k] = key;
setIndex(key, k);
}
/**
* Resize the heap array. Call only when holding lock.
*/
private void grow() {
int oldCapacity = queue.length;
int newCapacity = oldCapacity + (oldCapacity >> 1); // grow 50%
if (newCapacity < 0) // overflow
newCapacity = Integer.MAX_VALUE;
queue = Arrays.copyOf(queue, newCapacity);
}
/**
* Find index of given object, or -1 if absent
*/
private int indexOf(Object x) {
if (x != null) {
if (x instanceof ScheduledFutureTask) {
int i = ((ScheduledFutureTask) x).heapIndex;
// Sanity check; x could conceivably be a
// ScheduledFutureTask from some other pool.
if (i >= 0 && i < size && queue[i] == x)
return i;
} else {
for (int i = 0; i < size; i++)
if (x.equals(queue[i]))
return i;
}
}
return -1;
}
public boolean contains(Object x) {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return indexOf(x) != -1;
} finally {
lock.unlock();
}
}
public boolean remove(Object x) {
final ReentrantLock lock = this.lock;
lock.lock();
try {
int i = indexOf(x);
if (i < 0)
return false;
setIndex(queue[i], -1);
int s = --size;
RunnableScheduledFuture replacement = queue[s];
queue[s] = null;
if (s != i) {
siftDown(i, replacement);
if (queue[i] == replacement)
siftUp(i, replacement);
}
return true;
} finally {
lock.unlock();
}
}
public int size() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return size;
} finally {
lock.unlock();
}
}
public boolean isEmpty() {
return size() == 0;
}
public boolean add(Runnable x) {
return dq.add((RunnableScheduledFuture)x);
public int remainingCapacity() {
return Integer.MAX_VALUE;
}
public RunnableScheduledFuture peek() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return queue[0];
} finally {
lock.unlock();
}
}
public boolean offer(Runnable x) {
return dq.offer((RunnableScheduledFuture)x);
if (x == null)
throw new NullPointerException();
RunnableScheduledFuture e = (RunnableScheduledFuture)x;
final ReentrantLock lock = this.lock;
lock.lock();
try {
int i = size;
if (i >= queue.length)
grow();
size = i + 1;
if (i == 0) {
queue[0] = e;
setIndex(e, 0);
} else {
siftUp(i, e);
}
if (queue[0] == e) {
leader = null;
available.signal();
}
} finally {
lock.unlock();
}
return true;
}
public void put(Runnable x) {
dq.put((RunnableScheduledFuture)x);
public void put(Runnable e) {
offer(e);
}
public boolean add(Runnable e) {
return offer(e);
}
public boolean offer(Runnable e, long timeout, TimeUnit unit) {
return offer(e);
}
public boolean offer(Runnable x, long timeout, TimeUnit unit) {
return dq.offer((RunnableScheduledFuture)x, timeout, unit);
/**
* Performs common bookkeeping for poll and take: Replaces
* first element with last and sifts it down. Call only when
* holding lock.
* @param f the task to remove and return
*/
private RunnableScheduledFuture finishPoll(RunnableScheduledFuture f) {
int s = --size;
RunnableScheduledFuture x = queue[s];
queue[s] = null;
if (s != 0)
siftDown(0, x);
setIndex(f, -1);
return f;
}
public RunnableScheduledFuture poll() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
RunnableScheduledFuture first = queue[0];
if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0)
return null;
else
return finishPoll(first);
} finally {
lock.unlock();
}
}
public RunnableScheduledFuture take() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
for (;;) {
RunnableScheduledFuture first = queue[0];
if (first == null)
available.await();
else {
long delay = first.getDelay(TimeUnit.NANOSECONDS);
if (delay <= 0)
return finishPoll(first);
else if (leader != null)
available.await();
else {
Thread thisThread = Thread.currentThread();
leader = thisThread;
try {
available.awaitNanos(delay);
} finally {
if (leader == thisThread)
leader = null;
}
}
}
}
} finally {
if (leader == null && queue[0] != null)
available.signal();
lock.unlock();
}
}
public RunnableScheduledFuture poll(long timeout, TimeUnit unit)
throws InterruptedException {
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
for (;;) {
RunnableScheduledFuture first = queue[0];
if (first == null) {
if (nanos <= 0)
return null;
else
nanos = available.awaitNanos(nanos);
} else {
long delay = first.getDelay(TimeUnit.NANOSECONDS);
if (delay <= 0)
return finishPoll(first);
if (nanos <= 0)
return null;
if (nanos < delay || leader != null)
nanos = available.awaitNanos(nanos);
else {
Thread thisThread = Thread.currentThread();
leader = thisThread;
try {
long timeLeft = available.awaitNanos(delay);
nanos -= delay - timeLeft;
} finally {
if (leader == thisThread)
leader = null;
}
}
}
}
} finally {
if (leader == null && queue[0] != null)
available.signal();
lock.unlock();
}
}
public void clear() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
for (int i = 0; i < size; i++) {
RunnableScheduledFuture t = queue[i];
if (t != null) {
queue[i] = null;
setIndex(t, -1);
}
}
size = 0;
} finally {
lock.unlock();
}
}
/**
* Return and remove first element only if it is expired.
* Used only by drainTo. Call only when holding lock.
*/
private RunnableScheduledFuture pollExpired() {
RunnableScheduledFuture first = queue[0];
if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0)
return null;
return finishPoll(first);
}
public int drainTo(Collection<? super Runnable> c) {
if (c == null)
throw new NullPointerException();
if (c == this)
throw new IllegalArgumentException();
final ReentrantLock lock = this.lock;
lock.lock();
try {
RunnableScheduledFuture first;
int n = 0;
while ((first = pollExpired()) != null) {
c.add(first);
++n;
}
return n;
} finally {
lock.unlock();
}
}
public Runnable remove() { return dq.remove(); }
public Runnable element() { return dq.element(); }
public void clear() { dq.clear(); }
public int drainTo(Collection<? super Runnable> c) { return dq.drainTo(c); }
public int drainTo(Collection<? super Runnable> c, int maxElements) {
return dq.drainTo(c, maxElements);
if (c == null)
throw new NullPointerException();
if (c == this)
throw new IllegalArgumentException();
if (maxElements <= 0)
return 0;
final ReentrantLock lock = this.lock;
lock.lock();
try {
RunnableScheduledFuture first;
int n = 0;
while (n < maxElements && (first = pollExpired()) != null) {
c.add(first);
++n;
}
return n;
} finally {
lock.unlock();
}
}
public Object[] toArray() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return Arrays.copyOf(queue, size, Object[].class);
} finally {
lock.unlock();
}
}
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
final ReentrantLock lock = this.lock;
lock.lock();
try {
if (a.length < size)
return (T[]) Arrays.copyOf(queue, size, a.getClass());
System.arraycopy(queue, 0, a, 0, size);
if (a.length > size)
a[size] = null;
return a;
} finally {
lock.unlock();
}
}
public int remainingCapacity() { return dq.remainingCapacity(); }
public boolean remove(Object x) { return dq.remove(x); }
public boolean contains(Object x) { return dq.contains(x); }
public int size() { return dq.size(); }
public boolean isEmpty() { return dq.isEmpty(); }
public Object[] toArray() { return dq.toArray(); }
public <T> T[] toArray(T[] array) { return dq.toArray(array); }
public Iterator<Runnable> iterator() {
return new Iterator<Runnable>() {
private Iterator<RunnableScheduledFuture> it = dq.iterator();
public boolean hasNext() { return it.hasNext(); }
public Runnable next() { return it.next(); }
public void remove() { it.remove(); }
};
return new Itr(Arrays.copyOf(queue, size));
}
/**
* Snapshot iterator that works off copy of underlying q array.
*/
private class Itr implements Iterator<Runnable> {
final RunnableScheduledFuture[] array;
int cursor = 0; // index of next element to return
int lastRet = -1; // index of last element, or -1 if no such
Itr(RunnableScheduledFuture[] array) {
this.array = array;
}
public boolean hasNext() {
return cursor < array.length;
}
public Runnable next() {
if (cursor >= array.length)
throw new NoSuchElementException();
lastRet = cursor;
return array[cursor++];
}
public void remove() {
if (lastRet < 0)
throw new IllegalStateException();
DelayedWorkQueue.this.remove(array[lastRet]);
lastRet = -1;
}
}
}
}
test/java/util/concurrent/ScheduledThreadPoolExecutor/BasicCancelTest.java 0 → 100644
浏览文件 @ d9898853
/*
* Copyright 2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
/*
* @test
* @bug 6602600
* @run main/othervm -Xmx8m BasicCancelTest
* @summary Check effectiveness of RemoveOnCancelPolicy
*/
import java.util.concurrent.*;
import java.util.Random;
/**
* Simple timer cancellation test. Submits tasks to a scheduled executor
* service and immediately cancels them.
*/
public class BasicCancelTest {
void checkShutdown(final ExecutorService es) {
final Runnable nop = new Runnable() {public void run() {}};
try {
if (new Random().nextBoolean()) {
check(es.isShutdown());
if (es instanceof ThreadPoolExecutor)
check(((ThreadPoolExecutor) es).isTerminating()
|| es.isTerminated());
THROWS(RejectedExecutionException.class,
new F(){void f(){es.execute(nop);}});
}
} catch (Throwable t) { unexpected(t); }
}
void checkTerminated(final ThreadPoolExecutor tpe) {
try {
checkShutdown(tpe);
check(tpe.getQueue().isEmpty());
check(tpe.isTerminated());
check(! tpe.isTerminating());
equal(tpe.getActiveCount(), 0);
equal(tpe.getPoolSize(), 0);
equal(tpe.getTaskCount(), tpe.getCompletedTaskCount());
check(tpe.awaitTermination(0, TimeUnit.SECONDS));
} catch (Throwable t) { unexpected(t); }
}
void test(String[] args) throws Throwable {
final ScheduledThreadPoolExecutor pool =
new ScheduledThreadPoolExecutor(1);
// Needed to avoid OOME
pool.setRemoveOnCancelPolicy(true);
final long moreThanYouCanChew = Runtime.getRuntime().freeMemory() / 4;
System.out.printf("moreThanYouCanChew=%d%n", moreThanYouCanChew);
Runnable noopTask = new Runnable() { public void run() {}};
for (long i = 0; i < moreThanYouCanChew; i++)
pool.schedule(noopTask, 10, TimeUnit.MINUTES).cancel(true);
pool.shutdown();
check(pool.awaitTermination(1L, TimeUnit.DAYS));
checkTerminated(pool);
equal(pool.getTaskCount(), 0L);
equal(pool.getCompletedTaskCount(), 0L);
}
//--------------------- Infrastructure ---------------------------
volatile int passed = 0, failed = 0;
void pass() {passed++;}
void fail() {failed++; Thread.dumpStack();}
void fail(String msg) {System.err.println(msg); fail();}
void unexpected(Throwable t) {failed++; t.printStackTrace();}
void check(boolean cond) {if (cond) pass(); else fail();}
void equal(Object x, Object y) {
if (x == null ? y == null : x.equals(y)) pass();
else fail(x + " not equal to " + y);}
public static void main(String[] args) throws Throwable {
new BasicCancelTest().instanceMain(args);}
void instanceMain(String[] args) throws Throwable {
try {test(args);} catch (Throwable t) {unexpected(t);}
System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
if (failed > 0) throw new AssertionError("Some tests failed");}
abstract class F {abstract void f() throws Throwable;}
void THROWS(Class<? extends Throwable> k, F... fs) {
for (F f : fs)
try {f.f(); fail("Expected " + k.getName() + " not thrown");}
catch (Throwable t) {
if (k.isAssignableFrom(t.getClass())) pass();
else unexpected(t);}}
}
test/java/util/concurrent/ScheduledThreadPoolExecutor/Stress.java 0 → 100644
浏览文件 @ d9898853
/*
* Copyright 2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
import java.util.concurrent.*;
/**
* This is not a regression test, but a stress benchmark test for
* 6602600: Fast removal of cancelled scheduled thread pool tasks
*
* This runs in the same wall clock time, but much reduced cpu time,
* with the changes for 6602600.
*/
public class Stress {
public static void main(String[] args) throws Throwable {
final CountDownLatch count = new CountDownLatch(1000);
final ScheduledThreadPoolExecutor pool =
new ScheduledThreadPoolExecutor(100);
pool.prestartAllCoreThreads();
final Runnable incTask = new Runnable() { public void run() {
count.countDown();
}};
pool.scheduleAtFixedRate(incTask, 0, 10, TimeUnit.MILLISECONDS);
count.await();
pool.shutdown();
pool.awaitTermination(1L, TimeUnit.DAYS);
}
}
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