|
1 |
| -/** |
2 |
| - * Copyright 2014 Netflix, Inc. |
3 |
| - * |
4 |
| - * Licensed under the Apache License, Version 2.0 (the "License"); you may not |
5 |
| - * use this file except in compliance with the License. You may obtain a copy of |
6 |
| - * the License at |
7 |
| - * |
8 |
| - * http://www.apache.org/licenses/LICENSE-2.0 |
9 |
| - * |
10 |
| - * Unless required by applicable law or agreed to in writing, software |
11 |
| - * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
12 |
| - * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
13 |
| - * License for the specific language governing permissions and limitations under |
14 |
| - * the License. |
15 |
| - */ |
16 |
| -package rx.observers; |
17 |
| - |
18 |
| -import java.util.concurrent.atomic.AtomicReference; |
19 |
| -import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; |
20 |
| - |
21 |
| -/** |
22 |
| - * A multiple-producer single consumer queue implementation with padded reference |
23 |
| - * to tail to avoid cache-line thrashing. |
24 |
| - * Based on Netty's <a href='https://github.com/netty/netty/blob/master/common/src/main/java/io/netty/util/internal/MpscLinkedQueue.java'>MpscQueue implementation</a> but using AtomicReferenceFieldUpdater |
25 |
| - * instead of Unsafe. |
26 |
| - * @param <E> the element type |
27 |
| - */ |
28 |
| -public final class MpscPaddedQueue<E> extends AtomicReference<MpscPaddedQueue.Node<E>> { |
29 |
| - @SuppressWarnings(value = "rawtypes") |
30 |
| - static final AtomicReferenceFieldUpdater<PaddedNode, Node> TAIL_UPDATER = AtomicReferenceFieldUpdater.newUpdater(PaddedNode.class, Node.class, "tail"); |
31 |
| - /** */ |
32 |
| - private static final long serialVersionUID = 1L; |
33 |
| - /** The padded tail reference. */ |
34 |
| - final PaddedNode<E> tail; |
35 |
| - /** |
36 |
| - * Initializes the empty queue. |
37 |
| - */ |
38 |
| - public MpscPaddedQueue() { |
39 |
| - Node<E> first = new Node<E>(null); |
40 |
| - tail = new PaddedNode<E>(); |
41 |
| - tail.tail = first; |
42 |
| - set(first); |
43 |
| - } |
44 |
| - /** |
45 |
| - * Offer a new value. |
46 |
| - * @param v the value to offer |
47 |
| - */ |
48 |
| - public void offer(E v) { |
49 |
| - Node<E> n = new Node<E>(v); |
50 |
| - getAndSet(n).set(n); |
51 |
| - } |
52 |
| - |
53 |
| - /** |
54 |
| - * @return Poll a value from the head of the queue or return null if the queue is empty. |
55 |
| - */ |
56 |
| - public E poll() { |
57 |
| - Node<E> n = peekNode(); |
58 |
| - if (n == null) { |
59 |
| - return null; |
60 |
| - } |
61 |
| - E v = n.value; |
62 |
| - n.value = null; // do not retain this value as the node still stays in the queue |
63 |
| - TAIL_UPDATER.lazySet(tail, n); |
64 |
| - return v; |
65 |
| - } |
66 |
| - /** |
67 |
| - * Check if there is a node available without changing anything. |
68 |
| - */ |
69 |
| - private Node<E> peekNode() { |
70 |
| - for (;;) { |
71 |
| - @SuppressWarnings(value = "unchecked") |
72 |
| - Node<E> t = TAIL_UPDATER.get(tail); |
73 |
| - Node<E> n = t.get(); |
74 |
| - if (n != null || get() == t) { |
75 |
| - return n; |
76 |
| - } |
77 |
| - } |
78 |
| - } |
79 |
| - /** |
80 |
| - * Clears the queue. |
81 |
| - */ |
82 |
| - public void clear() { |
83 |
| - for (;;) { |
84 |
| - if (poll() == null) { |
85 |
| - break; |
86 |
| - } |
87 |
| - } |
88 |
| - } |
89 |
| - /** Class that contains a Node reference padded around to fit a typical cache line. */ |
90 |
| - static final class PaddedNode<E> { |
91 |
| - /** Padding, public to prevent optimizing it away. */ |
92 |
| - public int p1; |
93 |
| - volatile Node<E> tail; |
94 |
| - /** Padding, public to prevent optimizing it away. */ |
95 |
| - public long p2; |
96 |
| - /** Padding, public to prevent optimizing it away. */ |
97 |
| - public long p3; |
98 |
| - /** Padding, public to prevent optimizing it away. */ |
99 |
| - public long p4; |
100 |
| - /** Padding, public to prevent optimizing it away. */ |
101 |
| - public long p5; |
102 |
| - /** Padding, public to prevent optimizing it away. */ |
103 |
| - public long p6; |
104 |
| - } |
105 |
| - /** |
106 |
| - * Regular node with value and reference to the next node. |
107 |
| - */ |
108 |
| - static final class Node<E> { |
109 |
| - |
110 |
| - E value; |
111 |
| - @SuppressWarnings(value = "rawtypes") |
112 |
| - static final AtomicReferenceFieldUpdater<Node, Node> TAIL_UPDATER = AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "tail"); |
113 |
| - volatile Node<E> tail; |
114 |
| - |
115 |
| - public Node(E value) { |
116 |
| - this.value = value; |
117 |
| - } |
118 |
| - |
119 |
| - public void set(Node<E> newTail) { |
120 |
| - TAIL_UPDATER.lazySet(this, newTail); |
121 |
| - } |
122 |
| - |
123 |
| - @SuppressWarnings(value = "unchecked") |
124 |
| - public Node<E> get() { |
125 |
| - return TAIL_UPDATER.get(this); |
126 |
| - } |
127 |
| - } |
128 |
| - |
129 |
| -} |
| 1 | +/** |
| 2 | + * Copyright 2014 Netflix, Inc. |
| 3 | + * |
| 4 | + * Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| 5 | + * use this file except in compliance with the License. You may obtain a copy of |
| 6 | + * the License at |
| 7 | + * |
| 8 | + * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | + * |
| 10 | + * Unless required by applicable law or agreed to in writing, software |
| 11 | + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| 12 | + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| 13 | + * License for the specific language governing permissions and limitations under |
| 14 | + * the License. |
| 15 | + */ |
| 16 | +package rx.internal.util; |
| 17 | + |
| 18 | +import java.util.concurrent.atomic.AtomicReference; |
| 19 | +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; |
| 20 | + |
| 21 | +/** |
| 22 | + * A multiple-producer single consumer queue implementation with padded reference |
| 23 | + * to tail to avoid cache-line thrashing. |
| 24 | + * Based on Netty's <a href='https://github.com/netty/netty/blob/master/common/src/main/java/io/netty/util/internal/MpscLinkedQueue.java'>MpscQueue implementation</a> but using AtomicReferenceFieldUpdater |
| 25 | + * instead of Unsafe. |
| 26 | + * @param <E> the element type |
| 27 | + */ |
| 28 | +public final class MpscPaddedQueue<E> extends AtomicReference<MpscPaddedQueue.Node<E>> { |
| 29 | + @SuppressWarnings(value = "rawtypes") |
| 30 | + static final AtomicReferenceFieldUpdater<PaddedNode, Node> TAIL_UPDATER = AtomicReferenceFieldUpdater.newUpdater(PaddedNode.class, Node.class, "tail"); |
| 31 | + /** */ |
| 32 | + private static final long serialVersionUID = 1L; |
| 33 | + /** The padded tail reference. */ |
| 34 | + final PaddedNode<E> tail; |
| 35 | + /** |
| 36 | + * Initializes the empty queue. |
| 37 | + */ |
| 38 | + public MpscPaddedQueue() { |
| 39 | + Node<E> first = new Node<E>(null); |
| 40 | + tail = new PaddedNode<E>(); |
| 41 | + tail.tail = first; |
| 42 | + set(first); |
| 43 | + } |
| 44 | + /** |
| 45 | + * Offer a new value. |
| 46 | + * @param v the value to offer |
| 47 | + */ |
| 48 | + public void offer(E v) { |
| 49 | + Node<E> n = new Node<E>(v); |
| 50 | + getAndSet(n).set(n); |
| 51 | + } |
| 52 | + |
| 53 | + /** |
| 54 | + * @return Poll a value from the head of the queue or return null if the queue is empty. |
| 55 | + */ |
| 56 | + public E poll() { |
| 57 | + Node<E> n = peekNode(); |
| 58 | + if (n == null) { |
| 59 | + return null; |
| 60 | + } |
| 61 | + E v = n.value; |
| 62 | + n.value = null; // do not retain this value as the node still stays in the queue |
| 63 | + TAIL_UPDATER.lazySet(tail, n); |
| 64 | + return v; |
| 65 | + } |
| 66 | + /** |
| 67 | + * Check if there is a node available without changing anything. |
| 68 | + */ |
| 69 | + private Node<E> peekNode() { |
| 70 | + for (;;) { |
| 71 | + @SuppressWarnings(value = "unchecked") |
| 72 | + Node<E> t = TAIL_UPDATER.get(tail); |
| 73 | + Node<E> n = t.get(); |
| 74 | + if (n != null || get() == t) { |
| 75 | + return n; |
| 76 | + } |
| 77 | + } |
| 78 | + } |
| 79 | + /** |
| 80 | + * Clears the queue. |
| 81 | + */ |
| 82 | + public void clear() { |
| 83 | + for (;;) { |
| 84 | + if (poll() == null) { |
| 85 | + break; |
| 86 | + } |
| 87 | + } |
| 88 | + } |
| 89 | + /** Class that contains a Node reference padded around to fit a typical cache line. */ |
| 90 | + static final class PaddedNode<E> { |
| 91 | + /** Padding, public to prevent optimizing it away. */ |
| 92 | + public int p1; |
| 93 | + volatile Node<E> tail; |
| 94 | + /** Padding, public to prevent optimizing it away. */ |
| 95 | + public long p2; |
| 96 | + /** Padding, public to prevent optimizing it away. */ |
| 97 | + public long p3; |
| 98 | + /** Padding, public to prevent optimizing it away. */ |
| 99 | + public long p4; |
| 100 | + /** Padding, public to prevent optimizing it away. */ |
| 101 | + public long p5; |
| 102 | + /** Padding, public to prevent optimizing it away. */ |
| 103 | + public long p6; |
| 104 | + } |
| 105 | + /** |
| 106 | + * Regular node with value and reference to the next node. |
| 107 | + */ |
| 108 | + static final class Node<E> { |
| 109 | + |
| 110 | + E value; |
| 111 | + @SuppressWarnings(value = "rawtypes") |
| 112 | + static final AtomicReferenceFieldUpdater<Node, Node> TAIL_UPDATER = AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "tail"); |
| 113 | + volatile Node<E> tail; |
| 114 | + |
| 115 | + public Node(E value) { |
| 116 | + this.value = value; |
| 117 | + } |
| 118 | + |
| 119 | + public void set(Node<E> newTail) { |
| 120 | + TAIL_UPDATER.lazySet(this, newTail); |
| 121 | + } |
| 122 | + |
| 123 | + @SuppressWarnings(value = "unchecked") |
| 124 | + public Node<E> get() { |
| 125 | + return TAIL_UPDATER.get(this); |
| 126 | + } |
| 127 | + } |
| 128 | + |
| 129 | +} |
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