org.jctools.queues.MpmcArrayQueue 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 org.jctools.queues;
import org.jctools.util.RangeUtil;
import static org.jctools.util.UnsafeAccess.UNSAFE;
import static org.jctools.util.UnsafeAccess.fieldOffset;
import static org.jctools.util.UnsafeLongArrayAccess.*;
import static org.jctools.util.UnsafeRefArrayAccess.*;
abstract class MpmcArrayQueueL1Pad extends ConcurrentSequencedCircularArrayQueue
{
byte b000,b001,b002,b003,b004,b005,b006,b007;// 8b
byte b010,b011,b012,b013,b014,b015,b016,b017;// 16b
byte b020,b021,b022,b023,b024,b025,b026,b027;// 24b
byte b030,b031,b032,b033,b034,b035,b036,b037;// 32b
byte b040,b041,b042,b043,b044,b045,b046,b047;// 40b
byte b050,b051,b052,b053,b054,b055,b056,b057;// 48b
byte b060,b061,b062,b063,b064,b065,b066,b067;// 56b
byte b070,b071,b072,b073,b074,b075,b076,b077;// 64b
byte b100,b101,b102,b103,b104,b105,b106,b107;// 72b
byte b110,b111,b112,b113,b114,b115,b116,b117;// 80b
byte b120,b121,b122,b123,b124,b125,b126,b127;// 88b
byte b130,b131,b132,b133,b134,b135,b136,b137;// 96b
byte b140,b141,b142,b143,b144,b145,b146,b147;//104b
byte b150,b151,b152,b153,b154,b155,b156,b157;//112b
byte b160,b161,b162,b163,b164,b165,b166,b167;//120b
// byte b170,b171,b172,b173,b174,b175,b176,b177;//128b
MpmcArrayQueueL1Pad(int capacity)
{
super(capacity);
}
}
//$gen:ordered-fields
abstract class MpmcArrayQueueProducerIndexField extends MpmcArrayQueueL1Pad
{
private final static long P_INDEX_OFFSET = fieldOffset(MpmcArrayQueueProducerIndexField.class, "producerIndex");
private volatile long producerIndex;
MpmcArrayQueueProducerIndexField(int capacity)
{
super(capacity);
}
@Override
public final long lvProducerIndex()
{
return producerIndex;
}
final boolean casProducerIndex(long expect, long newValue)
{
return UNSAFE.compareAndSwapLong(this, P_INDEX_OFFSET, expect, newValue);
}
}
abstract class MpmcArrayQueueL2Pad extends MpmcArrayQueueProducerIndexField
{
byte b000,b001,b002,b003,b004,b005,b006,b007;// 8b
byte b010,b011,b012,b013,b014,b015,b016,b017;// 16b
byte b020,b021,b022,b023,b024,b025,b026,b027;// 24b
byte b030,b031,b032,b033,b034,b035,b036,b037;// 32b
byte b040,b041,b042,b043,b044,b045,b046,b047;// 40b
byte b050,b051,b052,b053,b054,b055,b056,b057;// 48b
byte b060,b061,b062,b063,b064,b065,b066,b067;// 56b
byte b070,b071,b072,b073,b074,b075,b076,b077;// 64b
byte b100,b101,b102,b103,b104,b105,b106,b107;// 72b
byte b110,b111,b112,b113,b114,b115,b116,b117;// 80b
byte b120,b121,b122,b123,b124,b125,b126,b127;// 88b
byte b130,b131,b132,b133,b134,b135,b136,b137;// 96b
byte b140,b141,b142,b143,b144,b145,b146,b147;//104b
byte b150,b151,b152,b153,b154,b155,b156,b157;//112b
byte b160,b161,b162,b163,b164,b165,b166,b167;//120b
byte b170,b171,b172,b173,b174,b175,b176,b177;//128b
MpmcArrayQueueL2Pad(int capacity)
{
super(capacity);
}
}
//$gen:ordered-fields
abstract class MpmcArrayQueueConsumerIndexField extends MpmcArrayQueueL2Pad
{
private final static long C_INDEX_OFFSET = fieldOffset(MpmcArrayQueueConsumerIndexField.class, "consumerIndex");
private volatile long consumerIndex;
MpmcArrayQueueConsumerIndexField(int capacity)
{
super(capacity);
}
@Override
public final long lvConsumerIndex()
{
return consumerIndex;
}
final boolean casConsumerIndex(long expect, long newValue)
{
return UNSAFE.compareAndSwapLong(this, C_INDEX_OFFSET, expect, newValue);
}
}
abstract class MpmcArrayQueueL3Pad extends MpmcArrayQueueConsumerIndexField
{
byte b000,b001,b002,b003,b004,b005,b006,b007;// 8b
byte b010,b011,b012,b013,b014,b015,b016,b017;// 16b
byte b020,b021,b022,b023,b024,b025,b026,b027;// 24b
byte b030,b031,b032,b033,b034,b035,b036,b037;// 32b
byte b040,b041,b042,b043,b044,b045,b046,b047;// 40b
byte b050,b051,b052,b053,b054,b055,b056,b057;// 48b
byte b060,b061,b062,b063,b064,b065,b066,b067;// 56b
byte b070,b071,b072,b073,b074,b075,b076,b077;// 64b
byte b100,b101,b102,b103,b104,b105,b106,b107;// 72b
byte b110,b111,b112,b113,b114,b115,b116,b117;// 80b
byte b120,b121,b122,b123,b124,b125,b126,b127;// 88b
byte b130,b131,b132,b133,b134,b135,b136,b137;// 96b
byte b140,b141,b142,b143,b144,b145,b146,b147;//104b
byte b150,b151,b152,b153,b154,b155,b156,b157;//112b
byte b160,b161,b162,b163,b164,b165,b166,b167;//120b
byte b170,b171,b172,b173,b174,b175,b176,b177;//128b
MpmcArrayQueueL3Pad(int capacity)
{
super(capacity);
}
}
/**
* A Multi-Producer-Multi-Consumer queue based on a {@link org.jctools.queues.ConcurrentCircularArrayQueue}. This
* implies that any and all threads may call the offer/poll/peek methods and correctness is maintained.
* This implementation follows patterns documented on the package level for False Sharing protection.
* The algorithm for offer/poll is an adaptation of the one put forward by D. Vyukov (See here). The original
* algorithm uses an array of structs which should offer nice locality properties but is sadly not possible in
* Java (waiting on Value Types or similar). The alternative explored here utilizes 2 arrays, one for each
* field of the struct. There is a further alternative in the experimental project which uses iteration phase
* markers to achieve the same algo and is closer structurally to the original, but sadly does not perform as
* well as this implementation.
*
* Tradeoffs to keep in mind:
*
* - Padding for false sharing: counter fields and queue fields are all padded as well as either side of
* both arrays. We are trading memory to avoid false sharing(active and passive).
*
- 2 arrays instead of one: The algorithm requires an extra array of longs matching the size of the
* elements array. This is doubling/tripling the memory allocated for the buffer.
*
- Power of 2 capacity: Actual elements buffer (and sequence buffer) is the closest power of 2 larger or
* equal to the requested capacity.
*
*/
public class MpmcArrayQueue extends MpmcArrayQueueL3Pad
{
public static final int MAX_LOOK_AHEAD_STEP = Integer.getInteger("jctools.mpmc.max.lookahead.step", 4096);
private final int lookAheadStep;
public MpmcArrayQueue(final int capacity)
{
super(RangeUtil.checkGreaterThanOrEqual(capacity, 2, "capacity"));
lookAheadStep = Math.max(2, Math.min(capacity() / 4, MAX_LOOK_AHEAD_STEP));
}
@Override
public boolean offer(final E e)
{
if (null == e)
{
throw new NullPointerException();
}
final long mask = this.mask;
final long capacity = mask + 1;
final long[] sBuffer = sequenceBuffer;
long pIndex;
long seqOffset;
long seq;
long cIndex = Long.MIN_VALUE;// start with bogus value, hope we don't need it
do
{
pIndex = lvProducerIndex();
seqOffset = calcCircularLongElementOffset(pIndex, mask);
seq = lvLongElement(sBuffer, seqOffset);
// consumer has not moved this seq forward, it's as last producer left
if (seq < pIndex)
{
// Extra check required to ensure [Queue.offer == false iff queue is full]
if (pIndex - capacity >= cIndex && // test against cached cIndex
pIndex - capacity >= (cIndex = lvConsumerIndex())) // test against latest cIndex
{
return false;
}
else
{
seq = pIndex + 1; // (+) hack to make it go around again without CAS
}
}
}
while (seq > pIndex || // another producer has moved the sequence(or +)
!casProducerIndex(pIndex, pIndex + 1)); // failed to increment
// casProducerIndex ensures correct construction
spRefElement(buffer, calcCircularRefElementOffset(pIndex, mask), e);
// seq++;
soLongElement(sBuffer, seqOffset, pIndex + 1);
return true;
}
/**
* {@inheritDoc}
*
* Because return null indicates queue is empty we cannot simply rely on next element visibility for poll
* and must test producer index when next element is not visible.
*/
@Override
public E poll()
{
// local load of field to avoid repeated loads after volatile reads
final long[] sBuffer = sequenceBuffer;
final long mask = this.mask;
long cIndex;
long seq;
long seqOffset;
long expectedSeq;
long pIndex = -1; // start with bogus value, hope we don't need it
do
{
cIndex = lvConsumerIndex();
seqOffset = calcCircularLongElementOffset(cIndex, mask);
seq = lvLongElement(sBuffer, seqOffset);
expectedSeq = cIndex + 1;
if (seq < expectedSeq)
{
// slot has not been moved by producer
if (cIndex >= pIndex && // test against cached pIndex
cIndex == (pIndex = lvProducerIndex())) // update pIndex if we must
{
// strict empty check, this ensures [Queue.poll() == null iff isEmpty()]
return null;
}
else
{
seq = expectedSeq + 1; // trip another go around
}
}
}
while (seq > expectedSeq || // another consumer beat us to it
!casConsumerIndex(cIndex, cIndex + 1)); // failed the CAS
final long offset = calcCircularRefElementOffset(cIndex, mask);
final E e = lpRefElement(buffer, offset);
spRefElement(buffer, offset, null);
// i.e. seq += capacity
soLongElement(sBuffer, seqOffset, cIndex + mask + 1);
return e;
}
@Override
public E peek()
{
// local load of field to avoid repeated loads after volatile reads
final long[] sBuffer = sequenceBuffer;
final long mask = this.mask;
long cIndex;
long seq;
long seqOffset;
long expectedSeq;
long pIndex = -1; // start with bogus value, hope we don't need it
E e;
while (true)
{
cIndex = lvConsumerIndex();
seqOffset = calcCircularLongElementOffset(cIndex, mask);
seq = lvLongElement(sBuffer, seqOffset);
expectedSeq = cIndex + 1;
if (seq < expectedSeq)
{
// slot has not been moved by producer
if (cIndex >= pIndex && // test against cached pIndex
cIndex == (pIndex = lvProducerIndex())) // update pIndex if we must
{
// strict empty check, this ensures [Queue.poll() == null iff isEmpty()]
return null;
}
}
else if (seq == expectedSeq)
{
final long offset = calcCircularRefElementOffset(cIndex, mask);
e = lvRefElement(buffer, offset);
if (lvConsumerIndex() == cIndex)
return e;
}
}
}
@Override
public boolean relaxedOffer(E e)
{
if (null == e)
{
throw new NullPointerException();
}
final long mask = this.mask;
final long[] sBuffer = sequenceBuffer;
long pIndex;
long seqOffset;
long seq;
do
{
pIndex = lvProducerIndex();
seqOffset = calcCircularLongElementOffset(pIndex, mask);
seq = lvLongElement(sBuffer, seqOffset);
if (seq < pIndex)
{ // slot not cleared by consumer yet
return false;
}
}
while (seq > pIndex || // another producer has moved the sequence
!casProducerIndex(pIndex, pIndex + 1)); // failed to increment
// casProducerIndex ensures correct construction
spRefElement(buffer, calcCircularRefElementOffset(pIndex, mask), e);
soLongElement(sBuffer, seqOffset, pIndex + 1);
return true;
}
@Override
public E relaxedPoll()
{
final long[] sBuffer = sequenceBuffer;
final long mask = this.mask;
long cIndex;
long seqOffset;
long seq;
long expectedSeq;
do
{
cIndex = lvConsumerIndex();
seqOffset = calcCircularLongElementOffset(cIndex, mask);
seq = lvLongElement(sBuffer, seqOffset);
expectedSeq = cIndex + 1;
if (seq < expectedSeq)
{
return null;
}
}
while (seq > expectedSeq || // another consumer beat us to it
!casConsumerIndex(cIndex, cIndex + 1)); // failed the CAS
final long offset = calcCircularRefElementOffset(cIndex, mask);
final E e = lpRefElement(buffer, offset);
spRefElement(buffer, offset, null);
soLongElement(sBuffer, seqOffset, cIndex + mask + 1);
return e;
}
@Override
public E relaxedPeek()
{
// local load of field to avoid repeated loads after volatile reads
final long[] sBuffer = sequenceBuffer;
final long mask = this.mask;
long cIndex;
long seq;
long seqOffset;
long expectedSeq;
E e;
do
{
cIndex = lvConsumerIndex();
seqOffset = calcCircularLongElementOffset(cIndex, mask);
seq = lvLongElement(sBuffer, seqOffset);
expectedSeq = cIndex + 1;
if (seq < expectedSeq)
{
return null;
}
else if (seq == expectedSeq)
{
final long offset = calcCircularRefElementOffset(cIndex, mask);
e = lvRefElement(buffer, offset);
if (lvConsumerIndex() == cIndex)
return e;
}
}
while (true);
}
@Override
public int drain(Consumer c, int limit)
{
if (null == c)
throw new IllegalArgumentException("c is null");
if (limit < 0)
throw new IllegalArgumentException("limit is negative: " + limit);
if (limit == 0)
return 0;
final long[] sBuffer = sequenceBuffer;
final long mask = this.mask;
final E[] buffer = this.buffer;
final int maxLookAheadStep = Math.min(this.lookAheadStep, limit);
int consumed = 0;
while (consumed < limit)
{
final int remaining = limit - consumed;
final int lookAheadStep = Math.min(remaining, maxLookAheadStep);
final long cIndex = lvConsumerIndex();
final long lookAheadIndex = cIndex + lookAheadStep - 1;
final long lookAheadSeqOffset = calcCircularLongElementOffset(lookAheadIndex, mask);
final long lookAheadSeq = lvLongElement(sBuffer, lookAheadSeqOffset);
final long expectedLookAheadSeq = lookAheadIndex + 1;
if (lookAheadSeq == expectedLookAheadSeq && casConsumerIndex(cIndex, expectedLookAheadSeq))
{
for (int i = 0; i < lookAheadStep; i++)
{
final long index = cIndex + i;
final long seqOffset = calcCircularLongElementOffset(index, mask);
final long offset = calcCircularRefElementOffset(index, mask);
final long expectedSeq = index + 1;
while (lvLongElement(sBuffer, seqOffset) != expectedSeq)
{
}
final E e = lpRefElement(buffer, offset);
spRefElement(buffer, offset, null);
soLongElement(sBuffer, seqOffset, index + mask + 1);
c.accept(e);
}
consumed += lookAheadStep;
}
else
{
if (lookAheadSeq < expectedLookAheadSeq)
{
if (notAvailable(cIndex, mask, sBuffer, cIndex + 1))
{
return consumed;
}
}
return consumed + drainOneByOne(c, remaining);
}
}
return limit;
}
private int drainOneByOne(Consumer c, int limit)
{
final long[] sBuffer = sequenceBuffer;
final long mask = this.mask;
final E[] buffer = this.buffer;
long cIndex;
long seqOffset;
long seq;
long expectedSeq;
for (int i = 0; i < limit; i++)
{
do
{
cIndex = lvConsumerIndex();
seqOffset = calcCircularLongElementOffset(cIndex, mask);
seq = lvLongElement(sBuffer, seqOffset);
expectedSeq = cIndex + 1;
if (seq < expectedSeq)
{
return i;
}
}
while (seq > expectedSeq || // another consumer beat us to it
!casConsumerIndex(cIndex, cIndex + 1)); // failed the CAS
final long offset = calcCircularRefElementOffset(cIndex, mask);
final E e = lpRefElement(buffer, offset);
spRefElement(buffer, offset, null);
soLongElement(sBuffer, seqOffset, cIndex + mask + 1);
c.accept(e);
}
return limit;
}
@Override
public int fill(Supplier s, int limit)
{
if (null == s)
throw new IllegalArgumentException("supplier is null");
if (limit < 0)
throw new IllegalArgumentException("limit is negative:" + limit);
if (limit == 0)
return 0;
final long[] sBuffer = sequenceBuffer;
final long mask = this.mask;
final E[] buffer = this.buffer;
final int maxLookAheadStep = Math.min(this.lookAheadStep, limit);
int produced = 0;
while (produced < limit)
{
final int remaining = limit - produced;
final int lookAheadStep = Math.min(remaining, maxLookAheadStep);
final long pIndex = lvProducerIndex();
final long lookAheadIndex = pIndex + lookAheadStep - 1;
final long lookAheadSeqOffset = calcCircularLongElementOffset(lookAheadIndex, mask);
final long lookAheadSeq = lvLongElement(sBuffer, lookAheadSeqOffset);
final long expectedLookAheadSeq = lookAheadIndex;
if (lookAheadSeq == expectedLookAheadSeq && casProducerIndex(pIndex, expectedLookAheadSeq + 1))
{
for (int i = 0; i < lookAheadStep; i++)
{
final long index = pIndex + i;
final long seqOffset = calcCircularLongElementOffset(index, mask);
final long offset = calcCircularRefElementOffset(index, mask);
while (lvLongElement(sBuffer, seqOffset) != index)
{
}
// Ordered store ensures correct construction
soRefElement(buffer, offset, s.get());
soLongElement(sBuffer, seqOffset, index + 1);
}
produced += lookAheadStep;
}
else
{
if (lookAheadSeq < expectedLookAheadSeq)
{
if (notAvailable(pIndex, mask, sBuffer, pIndex))
{
return produced;
}
}
return produced + fillOneByOne(s, remaining);
}
}
return limit;
}
private boolean notAvailable(long index, long mask, long[] sBuffer, long expectedSeq)
{
final long seqOffset = calcCircularLongElementOffset(index, mask);
final long seq = lvLongElement(sBuffer, seqOffset);
if (seq < expectedSeq)
{
return true;
}
return false;
}
private int fillOneByOne(Supplier s, int limit)
{
final long[] sBuffer = sequenceBuffer;
final long mask = this.mask;
final E[] buffer = this.buffer;
long pIndex;
long seqOffset;
long seq;
for (int i = 0; i < limit; i++)
{
do
{
pIndex = lvProducerIndex();
seqOffset = calcCircularLongElementOffset(pIndex, mask);
seq = lvLongElement(sBuffer, seqOffset);
if (seq < pIndex)
{ // slot not cleared by consumer yet
return i;
}
}
while (seq > pIndex || // another producer has moved the sequence
!casProducerIndex(pIndex, pIndex + 1)); // failed to increment
// Ordered store ensures correct construction
soRefElement(buffer, calcCircularRefElementOffset(pIndex, mask), s.get());
soLongElement(sBuffer, seqOffset, pIndex + 1);
}
return limit;
}
@Override
public int drain(Consumer c)
{
return MessagePassingQueueUtil.drain(this, c);
}
@Override
public int fill(Supplier s)
{
return MessagePassingQueueUtil.fillBounded(this, s);
}
@Override
public void drain(Consumer c, WaitStrategy w, ExitCondition exit)
{
MessagePassingQueueUtil.drain(this, c, w, exit);
}
@Override
public void fill(Supplier s, WaitStrategy wait, ExitCondition exit)
{
MessagePassingQueueUtil.fill(this, s, wait, exit);
}
}