co.elastic.apm.agent.shaded.jctools.queues.atomic.BaseMpscLinkedAtomicArrayQueue 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 co.elastic.apm.agent.shaded.jctools.queues.atomic;
import co.elastic.apm.agent.shaded.jctools.queues.IndexedQueueSizeUtil.IndexedQueue;
import co.elastic.apm.agent.shaded.jctools.util.PortableJvmInfo;
import co.elastic.apm.agent.shaded.jctools.util.Pow2;
import co.elastic.apm.agent.shaded.jctools.util.RangeUtil;
import java.lang.reflect.Field;
import java.util.AbstractQueue;
import java.util.Iterator;
import static co.elastic.apm.agent.shaded.jctools.queues.atomic.LinkedAtomicArrayQueueUtil.length;
import static co.elastic.apm.agent.shaded.jctools.queues.atomic.LinkedAtomicArrayQueueUtil.modifiedCalcElementOffset;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import co.elastic.apm.agent.shaded.jctools.queues.MessagePassingQueue;
import co.elastic.apm.agent.shaded.jctools.queues.MessagePassingQueue.Supplier;
import co.elastic.apm.agent.shaded.jctools.queues.MessagePassingQueueUtil;
import co.elastic.apm.agent.shaded.jctools.queues.QueueProgressIndicators;
import co.elastic.apm.agent.shaded.jctools.queues.IndexedQueueSizeUtil;
import static co.elastic.apm.agent.shaded.jctools.queues.atomic.LinkedAtomicArrayQueueUtil.*;
import java.util.concurrent.atomic.AtomicReferenceArray;
import co.elastic.apm.agent.shaded.jctools.queues.MpmcArrayQueue;
/**
* NOTE: This class was automatically generated by co.elastic.apm.agent.shaded.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseMpscLinkedArrayQueue.java.
*/
abstract class BaseMpscLinkedAtomicArrayQueuePad1 extends AbstractQueue implements IndexedQueue {
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
}
/**
* NOTE: This class was automatically generated by co.elastic.apm.agent.shaded.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseMpscLinkedArrayQueue.java.
*/
abstract class BaseMpscLinkedAtomicArrayQueueProducerFields extends BaseMpscLinkedAtomicArrayQueuePad1 {
private static final AtomicLongFieldUpdater P_INDEX_UPDATER = AtomicLongFieldUpdater.newUpdater(BaseMpscLinkedAtomicArrayQueueProducerFields.class, "producerIndex");
protected volatile long producerIndex;
@Override
public final long lvProducerIndex() {
return producerIndex;
}
final void soProducerIndex(long newValue) {
P_INDEX_UPDATER.lazySet(this, newValue);
}
final boolean casProducerIndex(long expect, long newValue) {
return P_INDEX_UPDATER.compareAndSet(this, expect, newValue);
}
}
/**
* NOTE: This class was automatically generated by co.elastic.apm.agent.shaded.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseMpscLinkedArrayQueue.java.
*/
abstract class BaseMpscLinkedAtomicArrayQueuePad2 extends BaseMpscLinkedAtomicArrayQueueProducerFields {
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
}
/**
* NOTE: This class was automatically generated by co.elastic.apm.agent.shaded.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseMpscLinkedArrayQueue.java.
*/
abstract class BaseMpscLinkedAtomicArrayQueueConsumerFields extends BaseMpscLinkedAtomicArrayQueuePad2 {
private static final AtomicLongFieldUpdater C_INDEX_UPDATER = AtomicLongFieldUpdater.newUpdater(BaseMpscLinkedAtomicArrayQueueConsumerFields.class, "consumerIndex");
protected long consumerMask;
protected AtomicReferenceArray consumerBuffer;
protected volatile long consumerIndex;
@Override
public final long lvConsumerIndex() {
return consumerIndex;
}
final void soConsumerIndex(long newValue) {
C_INDEX_UPDATER.lazySet(this, newValue);
}
}
/**
* NOTE: This class was automatically generated by co.elastic.apm.agent.shaded.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseMpscLinkedArrayQueue.java.
*/
abstract class BaseMpscLinkedAtomicArrayQueuePad3 extends BaseMpscLinkedAtomicArrayQueueConsumerFields {
long p0, p1, p2, p3, p4, p5, p6, p7;
long p10, p11, p12, p13, p14, p15, p16, p17;
}
/**
* NOTE: This class was automatically generated by co.elastic.apm.agent.shaded.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseMpscLinkedArrayQueue.java.
*/
abstract class BaseMpscLinkedAtomicArrayQueueColdProducerFields extends BaseMpscLinkedAtomicArrayQueuePad3 {
private static final AtomicLongFieldUpdater P_LIMIT_UPDATER = AtomicLongFieldUpdater.newUpdater(BaseMpscLinkedAtomicArrayQueueColdProducerFields.class, "producerLimit");
private volatile long producerLimit;
protected long producerMask;
protected AtomicReferenceArray producerBuffer;
final long lvProducerLimit() {
return producerLimit;
}
final boolean casProducerLimit(long expect, long newValue) {
return P_LIMIT_UPDATER.compareAndSet(this, expect, newValue);
}
final void soProducerLimit(long newValue) {
P_LIMIT_UPDATER.lazySet(this, newValue);
}
}
/**
* NOTE: This class was automatically generated by co.elastic.apm.agent.shaded.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseMpscLinkedArrayQueue.java.
* An MPSC array queue which starts at initialCapacity and grows to maxCapacity in linked chunks
* of the initial size. The queue grows only when the current buffer is full and elements are not copied on
* resize, instead a link to the new buffer is stored in the old buffer for the consumer to follow.
*
* @param
*/
public abstract class BaseMpscLinkedAtomicArrayQueue extends BaseMpscLinkedAtomicArrayQueueColdProducerFields implements MessagePassingQueue, QueueProgressIndicators {
// No post padding here, subclasses must add
private static final Object JUMP = new Object();
private static final int CONTINUE_TO_P_INDEX_CAS = 0;
private static final int RETRY = 1;
private static final int QUEUE_FULL = 2;
private static final int QUEUE_RESIZE = 3;
/**
* @param initialCapacity the queue initial capacity. If chunk size is fixed this will be the chunk size.
* Must be 2 or more.
*/
public BaseMpscLinkedAtomicArrayQueue(final int initialCapacity) {
RangeUtil.checkGreaterThanOrEqual(initialCapacity, 2, "initialCapacity");
int p2capacity = Pow2.roundToPowerOfTwo(initialCapacity);
// leave lower bit of mask clear
long mask = (p2capacity - 1) << 1;
// need extra element to point at next array
AtomicReferenceArray buffer = allocate(p2capacity + 1);
producerBuffer = buffer;
producerMask = mask;
consumerBuffer = buffer;
consumerMask = mask;
// we know it's all empty to start with
soProducerLimit(mask);
}
@Override
public final Iterator iterator() {
throw new UnsupportedOperationException();
}
@Override
public final int size() {
// NOTE: because indices are on even numbers we cannot use the size util.
/*
* It is possible for a thread to be interrupted or reschedule between the read of the producer and
* consumer indices, therefore protection is required to ensure size is within valid range. In the
* event of concurrent polls/offers to this method the size is OVER estimated as we read consumer
* index BEFORE the producer index.
*/
long after = lvConsumerIndex();
long size;
while (true) {
final long before = after;
final long currentProducerIndex = lvProducerIndex();
after = lvConsumerIndex();
if (before == after) {
size = ((currentProducerIndex - after) >> 1);
break;
}
}
// indexed queues.
if (size > Integer.MAX_VALUE) {
return Integer.MAX_VALUE;
} else {
return (int) size;
}
}
@Override
public final boolean isEmpty() {
// nothing we can do to make this an exact method.
return (this.lvConsumerIndex() == this.lvProducerIndex());
}
@Override
public String toString() {
return this.getClass().getName();
}
@Override
public boolean offer(final E e) {
if (null == e) {
throw new NullPointerException();
}
long mask;
AtomicReferenceArray buffer;
long pIndex;
while (true) {
long producerLimit = lvProducerLimit();
pIndex = lvProducerIndex();
// lower bit is indicative of resize, if we see it we spin until it's cleared
if ((pIndex & 1) == 1) {
continue;
}
// pIndex is even (lower bit is 0) -> actual index is (pIndex >> 1)
// mask/buffer may get changed by resizing -> only use for array access after successful CAS.
mask = this.producerMask;
buffer = this.producerBuffer;
// assumption behind this optimization is that queue is almost always empty or near empty
if (producerLimit <= pIndex) {
int result = offerSlowPath(mask, pIndex, producerLimit);
switch(result) {
case CONTINUE_TO_P_INDEX_CAS:
break;
case RETRY:
continue;
case QUEUE_FULL:
return false;
case QUEUE_RESIZE:
resize(mask, buffer, pIndex, e);
return true;
}
}
if (casProducerIndex(pIndex, pIndex + 2)) {
break;
}
}
// INDEX visible before ELEMENT
final int offset = modifiedCalcElementOffset(pIndex, mask);
// release element e
soElement(buffer, offset, e);
return true;
}
/**
* {@inheritDoc}
*
* This implementation is correct for single consumer thread use only.
*/
@SuppressWarnings("unchecked")
@Override
public E poll() {
final AtomicReferenceArray buffer = consumerBuffer;
final long index = consumerIndex;
final long mask = consumerMask;
final int offset = modifiedCalcElementOffset(index, mask);
// LoadLoad
Object e = lvElement(buffer, offset);
if (e == null) {
if (index != lvProducerIndex()) {
// visible.
do {
e = lvElement(buffer, offset);
} while (e == null);
} else {
return null;
}
}
if (e == JUMP) {
final AtomicReferenceArray nextBuffer = getNextBuffer(buffer, mask);
return newBufferPoll(nextBuffer, index);
}
// release element null
soElement(buffer, offset, null);
// release cIndex
soConsumerIndex(index + 2);
return (E) e;
}
/**
* {@inheritDoc}
*
* This implementation is correct for single consumer thread use only.
*/
@SuppressWarnings("unchecked")
@Override
public E peek() {
final AtomicReferenceArray buffer = consumerBuffer;
final long index = consumerIndex;
final long mask = consumerMask;
final int offset = modifiedCalcElementOffset(index, mask);
// LoadLoad
Object e = lvElement(buffer, offset);
if (e == null && index != lvProducerIndex()) {
// check the producer index. If the queue is indeed not empty we spin until element is visible.
do {
e = lvElement(buffer, offset);
} while (e == null);
}
if (e == JUMP) {
return newBufferPeek(getNextBuffer(buffer, mask), index);
}
return (E) e;
}
/**
* We do not inline resize into this method because we do not resize on fill.
*/
private int offerSlowPath(long mask, long pIndex, long producerLimit) {
final long cIndex = lvConsumerIndex();
long bufferCapacity = getCurrentBufferCapacity(mask);
if (cIndex + bufferCapacity > pIndex) {
if (!casProducerLimit(producerLimit, cIndex + bufferCapacity)) {
// retry from top
return RETRY;
} else {
// continue to pIndex CAS
return CONTINUE_TO_P_INDEX_CAS;
}
} else // full and cannot grow
if (availableInQueue(pIndex, cIndex) <= 0) {
// offer should return false;
return QUEUE_FULL;
} else // grab index for resize -> set lower bit
if (casProducerIndex(pIndex, pIndex + 1)) {
// trigger a resize
return QUEUE_RESIZE;
} else {
// failed resize attempt, retry from top
return RETRY;
}
}
/**
* @return available elements in queue * 2
*/
protected abstract long availableInQueue(long pIndex, long cIndex);
@SuppressWarnings("unchecked")
private AtomicReferenceArray getNextBuffer(final AtomicReferenceArray buffer, final long mask) {
final int offset = nextArrayOffset(mask);
final AtomicReferenceArray nextBuffer = (AtomicReferenceArray) lvElement(buffer, offset);
soElement(buffer, offset, null);
return nextBuffer;
}
private int nextArrayOffset(long mask) {
return modifiedCalcElementOffset(mask + 2, Long.MAX_VALUE);
}
private E newBufferPoll(AtomicReferenceArray nextBuffer, long index) {
final int offset = newBufferAndOffset(nextBuffer, index);
// LoadLoad
final E n = lvElement(nextBuffer, offset);
if (n == null) {
throw new IllegalStateException("new buffer must have at least one element");
}
// StoreStore
soElement(nextBuffer, offset, null);
soConsumerIndex(index + 2);
return n;
}
private E newBufferPeek(AtomicReferenceArray nextBuffer, long index) {
final int offset = newBufferAndOffset(nextBuffer, index);
// LoadLoad
final E n = lvElement(nextBuffer, offset);
if (null == n) {
throw new IllegalStateException("new buffer must have at least one element");
}
return n;
}
private int newBufferAndOffset(AtomicReferenceArray nextBuffer, long index) {
consumerBuffer = nextBuffer;
consumerMask = (length(nextBuffer) - 2) << 1;
return modifiedCalcElementOffset(index, consumerMask);
}
@Override
public long currentProducerIndex() {
return lvProducerIndex() / 2;
}
@Override
public long currentConsumerIndex() {
return lvConsumerIndex() / 2;
}
@Override
public abstract int capacity();
@Override
public boolean relaxedOffer(E e) {
return offer(e);
}
@SuppressWarnings("unchecked")
@Override
public E relaxedPoll() {
final AtomicReferenceArray buffer = consumerBuffer;
final long index = consumerIndex;
final long mask = consumerMask;
final int offset = modifiedCalcElementOffset(index, mask);
// LoadLoad
Object e = lvElement(buffer, offset);
if (e == null) {
return null;
}
if (e == JUMP) {
final AtomicReferenceArray nextBuffer = getNextBuffer(buffer, mask);
return newBufferPoll(nextBuffer, index);
}
soElement(buffer, offset, null);
soConsumerIndex(index + 2);
return (E) e;
}
@SuppressWarnings("unchecked")
@Override
public E relaxedPeek() {
final AtomicReferenceArray buffer = consumerBuffer;
final long index = consumerIndex;
final long mask = consumerMask;
final int offset = modifiedCalcElementOffset(index, mask);
// LoadLoad
Object e = lvElement(buffer, offset);
if (e == JUMP) {
return newBufferPeek(getNextBuffer(buffer, mask), index);
}
return (E) e;
}
@Override
public int fill(Supplier s) {
// result is a long because we want to have a safepoint check at regular intervals
long result = 0;
final int capacity = capacity();
do {
final int filled = fill(s, PortableJvmInfo.RECOMENDED_OFFER_BATCH);
if (filled == 0) {
return (int) result;
}
result += filled;
} while (result <= capacity);
return (int) result;
}
@Override
public int fill(Supplier s, int batchSize) {
long mask;
AtomicReferenceArray buffer;
long pIndex;
int claimedSlots;
while (true) {
long producerLimit = lvProducerLimit();
pIndex = lvProducerIndex();
// lower bit is indicative of resize, if we see it we spin until it's cleared
if ((pIndex & 1) == 1) {
continue;
}
// pIndex is even (lower bit is 0) -> actual index is (pIndex >> 1)
// NOTE: mask/buffer may get changed by resizing -> only use for array access after successful CAS.
// Only by virtue offloading them between the lvProducerIndex and a successful casProducerIndex are they
// safe to use.
mask = this.producerMask;
buffer = this.producerBuffer;
// a successful CAS ties the ordering, lv(pIndex) -> [mask/buffer] -> cas(pIndex)
// we want 'limit' slots, but will settle for whatever is visible to 'producerLimit'
long batchIndex = Math.min(producerLimit, pIndex + 2 * batchSize);
if (pIndex >= producerLimit || producerLimit < batchIndex) {
int result = offerSlowPath(mask, pIndex, producerLimit);
switch(result) {
case CONTINUE_TO_P_INDEX_CAS:
// offer slow path verifies only one slot ahead, we cannot rely on indication here
case RETRY:
continue;
case QUEUE_FULL:
return 0;
case QUEUE_RESIZE:
resize(mask, buffer, pIndex, s.get());
return 1;
}
}
// claim limit slots at once
if (casProducerIndex(pIndex, batchIndex)) {
claimedSlots = (int) ((batchIndex - pIndex) / 2);
break;
}
}
for (int i = 0; i < claimedSlots; i++) {
final int offset = modifiedCalcElementOffset(pIndex + 2 * i, mask);
soElement(buffer, offset, s.get());
}
return claimedSlots;
}
@Override
public void fill(Supplier s, WaitStrategy w, ExitCondition exit) {
while (exit.keepRunning()) {
if (fill(s, PortableJvmInfo.RECOMENDED_OFFER_BATCH) == 0) {
int idleCounter = 0;
while (exit.keepRunning() && fill(s, PortableJvmInfo.RECOMENDED_OFFER_BATCH) == 0) {
idleCounter = w.idle(idleCounter);
}
}
}
}
@Override
public int drain(Consumer c) {
return drain(c, capacity());
}
@Override
public int drain(final Consumer c, final int limit) {
// Impl note: there are potentially some small gains to be had by manually inlining relaxedPoll() and hoisting
// reused fields out to reduce redundant reads.
int i = 0;
E m;
for (; i < limit && (m = relaxedPoll()) != null; i++) {
c.accept(m);
}
return i;
}
@Override
public void drain(Consumer c, WaitStrategy w, ExitCondition exit) {
int idleCounter = 0;
while (exit.keepRunning()) {
E e = relaxedPoll();
if (e == null) {
idleCounter = w.idle(idleCounter);
continue;
}
idleCounter = 0;
c.accept(e);
}
}
private void resize(long oldMask, AtomicReferenceArray oldBuffer, long pIndex, E e) {
int newBufferLength = getNextBufferSize(oldBuffer);
final AtomicReferenceArray newBuffer = allocate(newBufferLength);
producerBuffer = newBuffer;
final int newMask = (newBufferLength - 2) << 1;
producerMask = newMask;
final int offsetInOld = modifiedCalcElementOffset(pIndex, oldMask);
final int offsetInNew = modifiedCalcElementOffset(pIndex, newMask);
// element in new array
soElement(newBuffer, offsetInNew, e);
// buffer linked
soElement(oldBuffer, nextArrayOffset(oldMask), newBuffer);
// ASSERT code
final long cIndex = lvConsumerIndex();
final long availableInQueue = availableInQueue(pIndex, cIndex);
RangeUtil.checkPositive(availableInQueue, "availableInQueue");
// Invalidate racing CASs
// We never set the limit beyond the bounds of a buffer
soProducerLimit(pIndex + Math.min(newMask, availableInQueue));
// make resize visible to the other producers
soProducerIndex(pIndex + 2);
// INDEX visible before ELEMENT, consistent with consumer expectation
// make resize visible to consumer
soElement(oldBuffer, offsetInOld, JUMP);
}
/**
* @return next buffer size(inclusive of next array pointer)
*/
protected abstract int getNextBufferSize(AtomicReferenceArray buffer);
/**
* @return current buffer capacity for elements (excluding next pointer and jump entry) * 2
*/
protected abstract long getCurrentBufferCapacity(long mask);
}