559 lines
27 KiB
C#
559 lines
27 KiB
C#
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// Copyright (c) Microsoft. All rights reserved.
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// Licensed under the MIT license. See LICENSE file in the project root for full license information.
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// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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//
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// ProducerConsumerQueues.cs
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//
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//
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// Specialized producer/consumer queues.
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//
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//
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// ************<IMPORTANT NOTE>*************
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//
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// There are two exact copies of this file:
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// src\ndp\clr\src\bcl\system\threading\tasks\producerConsumerQueue.cs
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// src\ndp\fx\src\dataflow\system\threading\tasks\dataflow\internal\producerConsumerQueue.cs
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// Keep both of them consistent by changing the other file when you change this one, also avoid:
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// 1- To reference internal types in mscorlib
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// 2- To reference any dataflow specific types
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// This should be fixed post Dev11 when this class becomes public.
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//
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// ************</IMPORTANT NOTE>*************
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// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
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using System.Collections;
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#if CONCURRENT_COLLECTIONS
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using System.Collections.Concurrent;
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#else
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using System.Threading.Tasks.Dataflow.Internal.Collections;
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#endif
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using System.Collections.Generic;
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using System.Diagnostics;
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using System.Diagnostics.Contracts;
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using System.Runtime.InteropServices;
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namespace System.Threading.Tasks
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{
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/// <summary>Represents a producer/consumer queue used internally by dataflow blocks.</summary>
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/// <typeparam name="T">Specifies the type of data contained in the queue.</typeparam>
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internal interface IProducerConsumerQueue<T> : IEnumerable<T>
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{
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/// <summary>Enqueues an item into the queue.</summary>
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/// <param name="item">The item to enqueue.</param>
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/// <remarks>This method is meant to be thread-safe subject to the particular nature of the implementation.</remarks>
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void Enqueue(T item);
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/// <summary>Attempts to dequeue an item from the queue.</summary>
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/// <param name="result">The dequeued item.</param>
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/// <returns>true if an item could be dequeued; otherwise, false.</returns>
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/// <remarks>This method is meant to be thread-safe subject to the particular nature of the implementation.</remarks>
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bool TryDequeue(out T result);
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/// <summary>Gets whether the collection is currently empty.</summary>
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/// <remarks>This method may or may not be thread-safe.</remarks>
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bool IsEmpty { get; }
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/// <summary>Gets the number of items in the collection.</summary>
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/// <remarks>In many implementations, this method will not be thread-safe.</remarks>
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int Count { get; }
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/// <summary>A thread-safe way to get the number of items in the collection. May synchronize access by locking the provided synchronization object.</summary>
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/// <param name="syncObj">The sync object used to lock</param>
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/// <returns>The collection count</returns>
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int GetCountSafe(object syncObj);
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}
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/// <summary>
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/// Provides a producer/consumer queue safe to be used by any number of producers and consumers concurrently.
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/// </summary>
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/// <typeparam name="T">Specifies the type of data contained in the queue.</typeparam>
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[DebuggerDisplay("Count = {Count}")]
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internal sealed class MultiProducerMultiConsumerQueue<T> : ConcurrentQueue<T>, IProducerConsumerQueue<T>
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{
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/// <summary>Enqueues an item into the queue.</summary>
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/// <param name="item">The item to enqueue.</param>
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void IProducerConsumerQueue<T>.Enqueue(T item) { base.Enqueue(item); }
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/// <summary>Attempts to dequeue an item from the queue.</summary>
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/// <param name="result">The dequeued item.</param>
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/// <returns>true if an item could be dequeued; otherwise, false.</returns>
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bool IProducerConsumerQueue<T>.TryDequeue(out T result) { return base.TryDequeue(out result); }
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/// <summary>Gets whether the collection is currently empty.</summary>
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bool IProducerConsumerQueue<T>.IsEmpty { get { return base.IsEmpty; } }
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/// <summary>Gets the number of items in the collection.</summary>
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int IProducerConsumerQueue<T>.Count { get { return base.Count; } }
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/// <summary>A thread-safe way to get the number of items in the collection. May synchronize access by locking the provided synchronization object.</summary>
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/// <remarks>ConcurrentQueue.Count is thread safe, no need to acquire the lock.</remarks>
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int IProducerConsumerQueue<T>.GetCountSafe(object syncObj) { return base.Count; }
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}
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/// <summary>
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/// Provides a producer/consumer queue safe to be used by only one producer and one consumer concurrently.
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/// </summary>
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/// <typeparam name="T">Specifies the type of data contained in the queue.</typeparam>
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[DebuggerDisplay("Count = {Count}")]
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[DebuggerTypeProxy(typeof(SingleProducerSingleConsumerQueue<>.SingleProducerSingleConsumerQueue_DebugView))]
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internal sealed class SingleProducerSingleConsumerQueue<T> : IProducerConsumerQueue<T>
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{
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// Design:
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//
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// SingleProducerSingleConsumerQueue (SPSCQueue) is a concurrent queue designed to be used
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// by one producer thread and one consumer thread. SPSCQueue does not work correctly when used by
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// multiple producer threads concurrently or multiple consumer threads concurrently.
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//
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// SPSCQueue is based on segments that behave like circular buffers. Each circular buffer is represented
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// as an array with two indexes: _first and _last. _first is the index of the array slot for the consumer
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// to read next, and _last is the slot for the producer to write next. The circular buffer is empty when
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// (_first == _last), and full when ((_last+1) % _array.Length == _first).
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//
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// Since _first is only ever modified by the consumer thread and _last by the producer, the two indices can
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// be updated without interlocked operations. As long as the queue size fits inside a single circular buffer,
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// enqueues and dequeues simply advance the corresponding indices around the circular buffer. If an enqueue finds
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// that there is no room in the existing buffer, however, a new circular buffer is allocated that is twice as big
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// as the old buffer. From then on, the producer will insert values into the new buffer. The consumer will first
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// empty out the old buffer and only then follow the producer into the new (larger) buffer.
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//
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// As described above, the enqueue operation on the fast path only modifies the _first field of the current segment.
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// However, it also needs to read _last in order to verify that there is room in the current segment. Similarly, the
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// dequeue operation on the fast path only needs to modify _last, but also needs to read _first to verify that the
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// queue is non-empty. This results in true cache line sharing between the producer and the consumer.
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//
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// The cache line sharing issue can be mitigating by having a possibly stale copy of _first that is owned by the producer,
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// and a possibly stale copy of _last that is owned by the consumer. So, the consumer state is described using
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// (_first, _lastCopy) and the producer state using (_firstCopy, _last). The consumer state is separated from
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// the producer state by padding, which allows fast-path enqueues and dequeues from hitting shared cache lines.
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// _lastCopy is the consumer's copy of _last. Whenever the consumer can tell that there is room in the buffer
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// simply by observing _lastCopy, the consumer thread does not need to read _last and thus encounter a cache miss. Only
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// when the buffer appears to be empty will the consumer refresh _lastCopy from _last. _firstCopy is used by the producer
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// in the same way to avoid reading _first on the hot path.
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/// <summary>The initial size to use for segments (in number of elements).</summary>
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private const int INIT_SEGMENT_SIZE = 32; // must be a power of 2
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/// <summary>The maximum size to use for segments (in number of elements).</summary>
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private const int MAX_SEGMENT_SIZE = 0x1000000; // this could be made as large as Int32.MaxValue / 2
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/// <summary>The head of the linked list of segments.</summary>
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private volatile Segment _head;
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/// <summary>The tail of the linked list of segments.</summary>
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private volatile Segment _tail;
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/// <summary>Initializes the queue.</summary>
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internal SingleProducerSingleConsumerQueue()
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{
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// Validate constants in ctor rather than in an explicit cctor that would cause perf degradation
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Debug.Assert(INIT_SEGMENT_SIZE > 0, "Initial segment size must be > 0.");
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Debug.Assert((INIT_SEGMENT_SIZE & (INIT_SEGMENT_SIZE - 1)) == 0, "Initial segment size must be a power of 2");
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Debug.Assert(INIT_SEGMENT_SIZE <= MAX_SEGMENT_SIZE, "Initial segment size should be <= maximum.");
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Debug.Assert(MAX_SEGMENT_SIZE < Int32.MaxValue / 2, "Max segment size * 2 must be < Int32.MaxValue, or else overflow could occur.");
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// Initialize the queue
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_head = _tail = new Segment(INIT_SEGMENT_SIZE);
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}
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/// <summary>Enqueues an item into the queue.</summary>
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/// <param name="item">The item to enqueue.</param>
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public void Enqueue(T item)
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{
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Segment segment = _tail;
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T[] array = segment._array;
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int last = segment._state._last; // local copy to avoid multiple volatile reads
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// Fast path: there's obviously room in the current segment
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int tail2 = (last + 1) & (array.Length - 1);
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if (tail2 != segment._state._firstCopy)
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{
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array[last] = item;
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segment._state._last = tail2;
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}
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// Slow path: there may not be room in the current segment.
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else EnqueueSlow(item, ref segment);
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}
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/// <summary>Enqueues an item into the queue.</summary>
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/// <param name="item">The item to enqueue.</param>
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/// <param name="segment">The segment in which to first attempt to store the item.</param>
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private void EnqueueSlow(T item, ref Segment segment)
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{
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Contract.Requires(segment != null, "Expected a non-null segment.");
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if (segment._state._firstCopy != segment._state._first)
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{
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segment._state._firstCopy = segment._state._first;
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Enqueue(item); // will only recur once for this enqueue operation
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return;
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}
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int newSegmentSize = _tail._array.Length << 1; // double size
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Debug.Assert(newSegmentSize > 0, "The max size should always be small enough that we don't overflow.");
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if (newSegmentSize > MAX_SEGMENT_SIZE) newSegmentSize = MAX_SEGMENT_SIZE;
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var newSegment = new Segment(newSegmentSize);
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newSegment._array[0] = item;
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newSegment._state._last = 1;
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newSegment._state._lastCopy = 1;
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try { }
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finally
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{
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// Finally block to protect against corruption due to a thread abort
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// between setting _next and setting _tail.
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Volatile.Write(ref _tail._next, newSegment); // ensure segment not published until item is fully stored
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_tail = newSegment;
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}
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}
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/// <summary>Attempts to dequeue an item from the queue.</summary>
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/// <param name="result">The dequeued item.</param>
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/// <returns>true if an item could be dequeued; otherwise, false.</returns>
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public bool TryDequeue(out T result)
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{
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Segment segment = _head;
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T[] array = segment._array;
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int first = segment._state._first; // local copy to avoid multiple volatile reads
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// Fast path: there's obviously data available in the current segment
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if (first != segment._state._lastCopy)
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{
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result = array[first];
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array[first] = default(T); // Clear the slot to release the element
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segment._state._first = (first + 1) & (array.Length - 1);
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return true;
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}
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// Slow path: there may not be data available in the current segment
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else return TryDequeueSlow(ref segment, ref array, out result);
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}
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/// <summary>Attempts to dequeue an item from the queue.</summary>
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/// <param name="array">The array from which the item was dequeued.</param>
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/// <param name="segment">The segment from which the item was dequeued.</param>
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/// <param name="result">The dequeued item.</param>
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/// <returns>true if an item could be dequeued; otherwise, false.</returns>
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private bool TryDequeueSlow(ref Segment segment, ref T[] array, out T result)
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{
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Contract.Requires(segment != null, "Expected a non-null segment.");
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Contract.Requires(array != null, "Expected a non-null item array.");
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if (segment._state._last != segment._state._lastCopy)
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{
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segment._state._lastCopy = segment._state._last;
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return TryDequeue(out result); // will only recur once for this dequeue operation
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}
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if (segment._next != null && segment._state._first == segment._state._last)
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{
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segment = segment._next;
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array = segment._array;
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_head = segment;
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}
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int first = segment._state._first; // local copy to avoid extraneous volatile reads
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if (first == segment._state._last)
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{
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result = default(T);
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return false;
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}
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result = array[first];
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array[first] = default(T); // Clear the slot to release the element
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segment._state._first = (first + 1) & (segment._array.Length - 1);
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segment._state._lastCopy = segment._state._last; // Refresh _lastCopy to ensure that _first has not passed _lastCopy
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return true;
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}
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/// <summary>Attempts to peek at an item in the queue.</summary>
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/// <param name="result">The peeked item.</param>
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/// <returns>true if an item could be peeked; otherwise, false.</returns>
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public bool TryPeek(out T result)
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{
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Segment segment = _head;
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T[] array = segment._array;
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int first = segment._state._first; // local copy to avoid multiple volatile reads
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// Fast path: there's obviously data available in the current segment
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if (first != segment._state._lastCopy)
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{
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result = array[first];
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return true;
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}
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// Slow path: there may not be data available in the current segment
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else return TryPeekSlow(ref segment, ref array, out result);
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}
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/// <summary>Attempts to peek at an item in the queue.</summary>
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/// <param name="array">The array from which the item is peeked.</param>
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/// <param name="segment">The segment from which the item is peeked.</param>
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/// <param name="result">The peeked item.</param>
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/// <returns>true if an item could be peeked; otherwise, false.</returns>
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private bool TryPeekSlow(ref Segment segment, ref T[] array, out T result)
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{
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Contract.Requires(segment != null, "Expected a non-null segment.");
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Contract.Requires(array != null, "Expected a non-null item array.");
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if (segment._state._last != segment._state._lastCopy)
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{
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segment._state._lastCopy = segment._state._last;
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return TryPeek(out result); // will only recur once for this peek operation
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}
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if (segment._next != null && segment._state._first == segment._state._last)
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{
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segment = segment._next;
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array = segment._array;
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_head = segment;
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}
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int first = segment._state._first; // local copy to avoid extraneous volatile reads
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if (first == segment._state._last)
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{
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|
|
result = default(T);
|
|||
|
|
return false;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
result = array[first];
|
|||
|
|
return true;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>Attempts to dequeue an item from the queue.</summary>
|
|||
|
|
/// <param name="predicate">The predicate that must return true for the item to be dequeued. If null, all items implicitly return true.</param>
|
|||
|
|
/// <param name="result">The dequeued item.</param>
|
|||
|
|
/// <returns>true if an item could be dequeued; otherwise, false.</returns>
|
|||
|
|
public bool TryDequeueIf(Predicate<T> predicate, out T result)
|
|||
|
|
{
|
|||
|
|
Segment segment = _head;
|
|||
|
|
T[] array = segment._array;
|
|||
|
|
int first = segment._state._first; // local copy to avoid multiple volatile reads
|
|||
|
|
|
|||
|
|
// Fast path: there's obviously data available in the current segment
|
|||
|
|
if (first != segment._state._lastCopy)
|
|||
|
|
{
|
|||
|
|
result = array[first];
|
|||
|
|
if (predicate == null || predicate(result))
|
|||
|
|
{
|
|||
|
|
array[first] = default(T); // Clear the slot to release the element
|
|||
|
|
segment._state._first = (first + 1) & (array.Length - 1);
|
|||
|
|
return true;
|
|||
|
|
}
|
|||
|
|
else
|
|||
|
|
{
|
|||
|
|
result = default(T);
|
|||
|
|
return false;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
// Slow path: there may not be data available in the current segment
|
|||
|
|
else return TryDequeueIfSlow(predicate, ref segment, ref array, out result);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>Attempts to dequeue an item from the queue.</summary>
|
|||
|
|
/// <param name="predicate">The predicate that must return true for the item to be dequeued. If null, all items implicitly return true.</param>
|
|||
|
|
/// <param name="array">The array from which the item was dequeued.</param>
|
|||
|
|
/// <param name="segment">The segment from which the item was dequeued.</param>
|
|||
|
|
/// <param name="result">The dequeued item.</param>
|
|||
|
|
/// <returns>true if an item could be dequeued; otherwise, false.</returns>
|
|||
|
|
private bool TryDequeueIfSlow(Predicate<T> predicate, ref Segment segment, ref T[] array, out T result)
|
|||
|
|
{
|
|||
|
|
Contract.Requires(segment != null, "Expected a non-null segment.");
|
|||
|
|
Contract.Requires(array != null, "Expected a non-null item array.");
|
|||
|
|
|
|||
|
|
if (segment._state._last != segment._state._lastCopy)
|
|||
|
|
{
|
|||
|
|
segment._state._lastCopy = segment._state._last;
|
|||
|
|
return TryDequeueIf(predicate, out result); // will only recur once for this dequeue operation
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
if (segment._next != null && segment._state._first == segment._state._last)
|
|||
|
|
{
|
|||
|
|
segment = segment._next;
|
|||
|
|
array = segment._array;
|
|||
|
|
_head = segment;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
int first = segment._state._first; // local copy to avoid extraneous volatile reads
|
|||
|
|
|
|||
|
|
if (first == segment._state._last)
|
|||
|
|
{
|
|||
|
|
result = default(T);
|
|||
|
|
return false;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
result = array[first];
|
|||
|
|
if (predicate == null || predicate(result))
|
|||
|
|
{
|
|||
|
|
array[first] = default(T); // Clear the slot to release the element
|
|||
|
|
segment._state._first = (first + 1) & (segment._array.Length - 1);
|
|||
|
|
segment._state._lastCopy = segment._state._last; // Refresh _lastCopy to ensure that _first has not passed _lastCopy
|
|||
|
|
return true;
|
|||
|
|
}
|
|||
|
|
else
|
|||
|
|
{
|
|||
|
|
result = default(T);
|
|||
|
|
return false;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
public void Clear()
|
|||
|
|
{
|
|||
|
|
T ignored;
|
|||
|
|
while (TryDequeue(out ignored)) ;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>Gets whether the collection is currently empty.</summary>
|
|||
|
|
/// <remarks>WARNING: This should not be used concurrently without further vetting.</remarks>
|
|||
|
|
public bool IsEmpty
|
|||
|
|
{
|
|||
|
|
// This implementation is optimized for calls from the consumer.
|
|||
|
|
get
|
|||
|
|
{
|
|||
|
|
Segment head = _head;
|
|||
|
|
if (head._state._first != head._state._lastCopy) return false; // _first is volatile, so the read of _lastCopy cannot get reordered
|
|||
|
|
if (head._state._first != head._state._last) return false;
|
|||
|
|
return head._next == null;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>Gets an enumerable for the collection.</summary>
|
|||
|
|
/// <remarks>WARNING: This should only be used for debugging purposes. It is not safe to be used concurrently.</remarks>
|
|||
|
|
public IEnumerator<T> GetEnumerator()
|
|||
|
|
{
|
|||
|
|
for (Segment segment = _head; segment != null; segment = segment._next)
|
|||
|
|
{
|
|||
|
|
for (int pt = segment._state._first;
|
|||
|
|
pt != segment._state._last;
|
|||
|
|
pt = (pt + 1) & (segment._array.Length - 1))
|
|||
|
|
{
|
|||
|
|
yield return segment._array[pt];
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
/// <summary>Gets an enumerable for the collection.</summary>
|
|||
|
|
/// <remarks>WARNING: This should only be used for debugging purposes. It is not safe to be used concurrently.</remarks>
|
|||
|
|
IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
|
|||
|
|
|
|||
|
|
/// <summary>Gets the number of items in the collection.</summary>
|
|||
|
|
/// <remarks>WARNING: This should only be used for debugging purposes. It is not meant to be used concurrently.</remarks>
|
|||
|
|
public int Count
|
|||
|
|
{
|
|||
|
|
get
|
|||
|
|
{
|
|||
|
|
int count = 0;
|
|||
|
|
for (Segment segment = _head; segment != null; segment = segment._next)
|
|||
|
|
{
|
|||
|
|
int arraySize = segment._array.Length;
|
|||
|
|
int first, last;
|
|||
|
|
while (true) // Count is not meant to be used concurrently, but this helps to avoid issues if it is
|
|||
|
|
{
|
|||
|
|
first = segment._state._first;
|
|||
|
|
last = segment._state._last;
|
|||
|
|
if (first == segment._state._first) break;
|
|||
|
|
}
|
|||
|
|
count += (last - first) & (arraySize - 1);
|
|||
|
|
}
|
|||
|
|
return count;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>A thread-safe way to get the number of items in the collection. May synchronize access by locking the provided synchronization object.</summary>
|
|||
|
|
/// <remarks>The Count is not thread safe, so we need to acquire the lock.</remarks>
|
|||
|
|
int IProducerConsumerQueue<T>.GetCountSafe(object syncObj)
|
|||
|
|
{
|
|||
|
|
Debug.Assert(syncObj != null, "The syncObj parameter is null.");
|
|||
|
|
lock (syncObj)
|
|||
|
|
{
|
|||
|
|
return Count;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>A segment in the queue containing one or more items.</summary>
|
|||
|
|
[StructLayout(LayoutKind.Sequential)]
|
|||
|
|
private sealed class Segment
|
|||
|
|
{
|
|||
|
|
/// <summary>The next segment in the linked list of segments.</summary>
|
|||
|
|
internal Segment _next;
|
|||
|
|
/// <summary>The data stored in this segment.</summary>
|
|||
|
|
internal readonly T[] _array;
|
|||
|
|
/// <summary>Details about the segment.</summary>
|
|||
|
|
internal SegmentState _state; // separated out to enable StructLayout attribute to take effect
|
|||
|
|
|
|||
|
|
/// <summary>Initializes the segment.</summary>
|
|||
|
|
/// <param name="size">The size to use for this segment.</param>
|
|||
|
|
internal Segment(int size)
|
|||
|
|
{
|
|||
|
|
Contract.Requires((size & (size - 1)) == 0, "Size must be a power of 2");
|
|||
|
|
_array = new T[size];
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>Stores information about a segment.</summary>
|
|||
|
|
[StructLayout(LayoutKind.Sequential)] // enforce layout so that padding reduces false sharing
|
|||
|
|
private struct SegmentState
|
|||
|
|
{
|
|||
|
|
/// <summary>Padding to reduce false sharing between the segment's array and _first.</summary>
|
|||
|
|
internal PaddingFor32 _pad0;
|
|||
|
|
|
|||
|
|
/// <summary>The index of the current head in the segment.</summary>
|
|||
|
|
internal volatile int _first;
|
|||
|
|
/// <summary>A copy of the current tail index.</summary>
|
|||
|
|
internal int _lastCopy; // not volatile as read and written by the producer, except for IsEmpty, and there _lastCopy is only read after reading the volatile _first
|
|||
|
|
|
|||
|
|
/// <summary>Padding to reduce false sharing between the first and last.</summary>
|
|||
|
|
internal PaddingFor32 _pad1;
|
|||
|
|
|
|||
|
|
/// <summary>A copy of the current head index.</summary>
|
|||
|
|
internal int _firstCopy; // not volatile as only read and written by the consumer thread
|
|||
|
|
/// <summary>The index of the current tail in the segment.</summary>
|
|||
|
|
internal volatile int _last;
|
|||
|
|
|
|||
|
|
/// <summary>Padding to reduce false sharing with the last and what's after the segment.</summary>
|
|||
|
|
internal PaddingFor32 _pad2;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>Debugger type proxy for a SingleProducerSingleConsumerQueue of T.</summary>
|
|||
|
|
private sealed class SingleProducerSingleConsumerQueue_DebugView
|
|||
|
|
{
|
|||
|
|
/// <summary>The queue being visualized.</summary>
|
|||
|
|
private readonly SingleProducerSingleConsumerQueue<T> _queue;
|
|||
|
|
|
|||
|
|
/// <summary>Initializes the debug view.</summary>
|
|||
|
|
/// <param name="queue">The queue being debugged.</param>
|
|||
|
|
public SingleProducerSingleConsumerQueue_DebugView(SingleProducerSingleConsumerQueue<T> queue)
|
|||
|
|
{
|
|||
|
|
Contract.Requires(queue != null, "Expected a non-null queue.");
|
|||
|
|
_queue = queue;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>Gets the contents of the list.</summary>
|
|||
|
|
[DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
|
|||
|
|
public T[] Items
|
|||
|
|
{
|
|||
|
|
get
|
|||
|
|
{
|
|||
|
|
List<T> list = new List<T>();
|
|||
|
|
foreach (T item in _queue)
|
|||
|
|
list.Add(item);
|
|||
|
|
return list.ToArray();
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
|
|||
|
|
/// <summary>A placeholder class for common padding constants and eventually routines.</summary>
|
|||
|
|
static class PaddingHelpers
|
|||
|
|
{
|
|||
|
|
/// <summary>A size greater than or equal to the size of the most common CPU cache lines.</summary>
|
|||
|
|
internal const int CACHE_LINE_SIZE = 128;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>Padding structure used to minimize false sharing in SingleProducerSingleConsumerQueue{T}.</summary>
|
|||
|
|
[StructLayout(LayoutKind.Explicit, Size = PaddingHelpers.CACHE_LINE_SIZE - sizeof(Int32))] // Based on common case of 64-byte cache lines
|
|||
|
|
struct PaddingFor32
|
|||
|
|
{
|
|||
|
|
}
|
|||
|
|
}
|