io.netty.util.internal.shaded.org.jctools.queues.SpscArrayQueue Maven / Gradle / Ivy
/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.netty.util.internal.shaded.org.jctools.queues;
import static io.netty.util.internal.shaded.org.jctools.util.UnsafeAccess.UNSAFE;
import static io.netty.util.internal.shaded.org.jctools.util.UnsafeRefArrayAccess.lvElement;
import static io.netty.util.internal.shaded.org.jctools.util.UnsafeRefArrayAccess.soElement;
abstract class SpscArrayQueueColdField extends ConcurrentCircularArrayQueue
{
public static final int MAX_LOOK_AHEAD_STEP = Integer.getInteger("jctools.spsc.max.lookahead.step", 4096);
protected final int lookAheadStep;
public SpscArrayQueueColdField(int capacity)
{
super(capacity);
lookAheadStep = Math.min(capacity() / 4, MAX_LOOK_AHEAD_STEP);
}
}
abstract class SpscArrayQueueL1Pad extends SpscArrayQueueColdField
{
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
public SpscArrayQueueL1Pad(int capacity)
{
super(capacity);
}
}
// $gen:ordered-fields
abstract class SpscArrayQueueProducerIndexFields extends SpscArrayQueueL1Pad
{
protected final static long P_INDEX_OFFSET;
static
{
try
{
P_INDEX_OFFSET =
UNSAFE.objectFieldOffset(SpscArrayQueueProducerIndexFields.class.getDeclaredField("producerIndex"));
}
catch (NoSuchFieldException e)
{
throw new RuntimeException(e);
}
}
protected long producerIndex;
protected long producerLimit;
public SpscArrayQueueProducerIndexFields(int capacity)
{
super(capacity);
}
@Override
public final long lvProducerIndex()
{
return UNSAFE.getLongVolatile(this, P_INDEX_OFFSET);
}
protected final void soProducerIndex(final long newValue)
{
UNSAFE.putOrderedLong(this, P_INDEX_OFFSET, newValue);
}
}
abstract class SpscArrayQueueL2Pad extends SpscArrayQueueProducerIndexFields
{
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
public SpscArrayQueueL2Pad(int capacity)
{
super(capacity);
}
}
//$gen:ordered-fields
abstract class SpscArrayQueueConsumerIndexField extends SpscArrayQueueL2Pad
{
protected long consumerIndex;
protected final static long C_INDEX_OFFSET;
static
{
try
{
C_INDEX_OFFSET =
UNSAFE.objectFieldOffset(SpscArrayQueueConsumerIndexField.class.getDeclaredField("consumerIndex"));
}
catch (NoSuchFieldException e)
{
throw new RuntimeException(e);
}
}
public SpscArrayQueueConsumerIndexField(int capacity)
{
super(capacity);
}
public final long lvConsumerIndex()
{
return UNSAFE.getLongVolatile(this, C_INDEX_OFFSET);
}
protected final void soConsumerIndex(final long newValue)
{
UNSAFE.putOrderedLong(this, C_INDEX_OFFSET, newValue);
}
}
abstract class SpscArrayQueueL3Pad extends SpscArrayQueueConsumerIndexField
{
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
public SpscArrayQueueL3Pad(int capacity)
{
super(capacity);
}
}
/**
* A Single-Producer-Single-Consumer queue backed by a pre-allocated buffer.
*
* This implementation is a mashup of the Fast Flow
* algorithm with an optimization of the offer method taken from the BQueue algorithm (a variation on Fast
* Flow), and adjusted to comply with Queue.offer semantics with regards to capacity.
* For convenience the relevant papers are available in the resources folder:
* 2010 - Pisa - SPSC Queues on Shared Cache Multi-Core Systems.pdf
* 2012 - Junchang- BQueue- Efficient and Practical Queuing.pdf
* This implementation is wait free.
*
* @param
* @author nitsanw
*/
public class SpscArrayQueue extends SpscArrayQueueL3Pad
{
public SpscArrayQueue(final int capacity)
{
super(Math.max(capacity, 4));
}
/**
* {@inheritDoc}
*
* This implementation is correct for single producer thread use only.
*/
@Override
public boolean offer(final E e)
{
if (null == e)
{
throw new NullPointerException();
}
// local load of field to avoid repeated loads after volatile reads
final E[] buffer = this.buffer;
final long mask = this.mask;
final long producerIndex = this.producerIndex;
if (producerIndex >= producerLimit &&
!offerSlowPath(buffer, mask, producerIndex))
{
return false;
}
final long offset = calcElementOffset(producerIndex, mask);
soElement(buffer, offset, e); // StoreStore
soProducerIndex(producerIndex + 1); // ordered store -> atomic and ordered for size()
return true;
}
private boolean offerSlowPath(final E[] buffer, final long mask, final long producerIndex)
{
final int lookAheadStep = this.lookAheadStep;
if (null == lvElement(buffer, calcElementOffset(producerIndex + lookAheadStep, mask)))
{// LoadLoad
producerLimit = producerIndex + lookAheadStep;
}
else
{
final long offset = calcElementOffset(producerIndex, mask);
if (null != lvElement(buffer, offset))
{
return false;
}
}
return true;
}
/**
* {@inheritDoc}
*
* This implementation is correct for single consumer thread use only.
*/
@Override
public E poll()
{
final long consumerIndex = this.consumerIndex;
final long offset = calcElementOffset(consumerIndex);
// local load of field to avoid repeated loads after volatile reads
final E[] buffer = this.buffer;
final E e = lvElement(buffer, offset);// LoadLoad
if (null == e)
{
return null;
}
soElement(buffer, offset, null);// StoreStore
soConsumerIndex(consumerIndex + 1); // ordered store -> atomic and ordered for size()
return e;
}
/**
* {@inheritDoc}
*
* This implementation is correct for single consumer thread use only.
*/
@Override
public E peek()
{
return lvElement(buffer, calcElementOffset(consumerIndex));
}
@Override
public boolean relaxedOffer(final E message)
{
return offer(message);
}
@Override
public E relaxedPoll()
{
return poll();
}
@Override
public E relaxedPeek()
{
return peek();
}
@Override
public int drain(final Consumer c)
{
return drain(c, capacity());
}
@Override
public int fill(final Supplier s)
{
return fill(s, capacity());
}
@Override
public int drain(final Consumer c, final int limit)
{
final E[] buffer = this.buffer;
final long mask = this.mask;
final long consumerIndex = this.consumerIndex;
for (int i = 0; i < limit; i++)
{
final long index = consumerIndex + i;
final long offset = calcElementOffset(index, mask);
final E e = lvElement(buffer, offset);// LoadLoad
if (null == e)
{
return i;
}
soElement(buffer, offset, null);// StoreStore
soConsumerIndex(index + 1); // ordered store -> atomic and ordered for size()
c.accept(e);
}
return limit;
}
@Override
public int fill(final Supplier s, final int limit)
{
final E[] buffer = this.buffer;
final long mask = this.mask;
final int lookAheadStep = this.lookAheadStep;
final long producerIndex = this.producerIndex;
for (int i = 0; i < limit; i++)
{
final long index = producerIndex + i;
final long lookAheadElementOffset = calcElementOffset(index + lookAheadStep, mask);
if (null == lvElement(buffer, lookAheadElementOffset))
{// LoadLoad
int lookAheadLimit = Math.min(lookAheadStep, limit - i);
for (int j = 0; j < lookAheadLimit; j++)
{
final long offset = calcElementOffset(index + j, mask);
soElement(buffer, offset, s.get()); // StoreStore
soProducerIndex(index + j + 1); // ordered store -> atomic and ordered for size()
}
i += lookAheadLimit - 1;
}
else
{
final long offset = calcElementOffset(index, mask);
if (null != lvElement(buffer, offset))
{
return i;
}
soElement(buffer, offset, s.get()); // StoreStore
soProducerIndex(index + 1); // ordered store -> atomic and ordered for size()
}
}
return limit;
}
@Override
public void drain(final Consumer c, final WaitStrategy w, final ExitCondition exit)
{
final E[] buffer = this.buffer;
final long mask = this.mask;
long consumerIndex = this.consumerIndex;
int counter = 0;
while (exit.keepRunning())
{
for (int i = 0; i < 4096; i++)
{
final long offset = calcElementOffset(consumerIndex, mask);
final E e = lvElement(buffer, offset);// LoadLoad
if (null == e)
{
counter = w.idle(counter);
continue;
}
consumerIndex++;
counter = 0;
soElement(buffer, offset, null);// StoreStore
soConsumerIndex(consumerIndex); // ordered store -> atomic and ordered for size()
c.accept(e);
}
}
}
@Override
public void fill(final Supplier s, final WaitStrategy w, final ExitCondition e)
{
final E[] buffer = this.buffer;
final long mask = this.mask;
final int lookAheadStep = this.lookAheadStep;
long producerIndex = this.producerIndex;
int counter = 0;
while (e.keepRunning())
{
final long lookAheadElementOffset = calcElementOffset(producerIndex + lookAheadStep, mask);
if (null == lvElement(buffer, lookAheadElementOffset))
{// LoadLoad
for (int j = 0; j < lookAheadStep; j++)
{
final long offset = calcElementOffset(producerIndex, mask);
producerIndex++;
soElement(buffer, offset, s.get()); // StoreStore
soProducerIndex(producerIndex); // ordered store -> atomic and ordered for size()
}
}
else
{
final long offset = calcElementOffset(producerIndex, mask);
if (null != lvElement(buffer, offset))
{// LoadLoad
counter = w.idle(counter);
continue;
}
producerIndex++;
counter = 0;
soElement(buffer, offset, s.get()); // StoreStore
soProducerIndex(producerIndex); // ordered store -> atomic and ordered for size()
}
}
}
}