136 lines
6.3 KiB
C#
136 lines
6.3 KiB
C#
//-----------------------------------------------------------------------
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// -----------------------------------------------------------------------
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// file="SlabAllocator"
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// Project: StgSharp
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// AuthorGroup: Nitload
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// Copyright (c) Nitload. All rights reserved.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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//
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// -----------------------------------------------------------------------
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// -----------------------------------------------------------------------
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using StgSharp.HighPerformance.Memory;
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using System;
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namespace StgSharp.HighPerformance.Memory
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{
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public static class SlabAllocator
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{
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/// <summary>
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/// Creates a new SLAB allocator instance with the specified configuration.
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/// </summary>
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/// <param name="count">
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/// Initial number of objects that can be allocated.
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/// </param>
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/// <param name="layout">
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/// Memory layout strategy for the SLAB allocator.
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/// </param>
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/// <param name="concurrentSupport">
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/// Whether to enable concurrent access support.
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/// </param>
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/// <returns>
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/// A new SLAB allocator instance.
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/// </returns>
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/// <exception cref="ArgumentOutOfRangeException">
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/// Thrown when an invalid layout is specified.
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/// </exception>
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/// <exception cref="NotSupportedException">
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/// Thrown when requesting unsupported configurations.
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/// </exception>
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/// <remarks>
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/// <para><strong> Important Threading Considerations: </strong></para> <para> While SLAB
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/// allocators themselves may be designed for single-threaded use, allocated objects are
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/// frequently shared across multiple threads in real-world applications. Due to the
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/// special implementation of expandable concurrent sequential SLAB allocators, they rely
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/// on internal expansion locks to ensure that memory buffer expansions (which involve
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/// copying the entire buffer to a new location) do not occur while other threads are
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/// reading from allocated regions.</para> <para><strong>Sequential Layout
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/// Limitations:</strong><br /> Sequential layout SLAB allocators cannot provide a single-
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/// threaded version because:<list type="bullet"><item><description>They use contiguous
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/// memory layout that requires buffer expansion when capacity is
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/// exceeded</description></item><item><description>Buffer expansion involves copying all
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/// existing data to a new memory location</description></item><item><description> Without
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/// proper synchronization, concurrent access to allocated objects during synchronization,
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/// concurrent access to allocated objects during expansion would cause memory corruption
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/// </description></item><item><description> The expansion lock mechanism is essential
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/// even if allocation itself is single- threaded</description></item></list></para>
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/// <para><strong> Chunked Layout: </strong><br /> Chunked layout allocators can
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/// optionally provide single-threaded versions since they don't require buffer expansion
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/// and copying. Each chunk is allocated independently, avoiding the memory relocation
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/// issues present in sequential layouts.</para>
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/// </remarks>
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public static SlabAllocator<T> Create<T>(
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nuint count,
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SlabBufferLayout layout,
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bool concurrentSupport = true
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) where T : unmanaged
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{
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return layout switch
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{
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SlabBufferLayout.Sequential => concurrentSupport ?
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new ConcurrentSequentialSlabAllocator<T>(count) :
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throw (new NotSupportedException("Non-concurrent version of sequential layout SLAB is not supported due to expansion lock requirements for memory safety during buffer expansion.")),
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SlabBufferLayout.Chunked => concurrentSupport ?
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new ConcurrentChunkedSlabAllocator<T>(count) :
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new ChunkedSlabAllocator<T>(count),
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_ => throw (new ArgumentOutOfRangeException(nameof(layout), layout, null))
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};
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static SlabAllocator<T> FromBuffer<T>(
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nuint buffer,
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nuint count,
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Action<nuint> freeHandle
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) where T : unmanaged
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{
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return new FixedSlabAllocator<T>(buffer, count, freeHandle);
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}
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}
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public abstract class SlabAllocator<T> : IDisposable where T : unmanaged
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{
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public abstract nuint Allocate();
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public abstract void Dispose();
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public abstract void EnterBufferReading();
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public abstract void ExitBufferReading();
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public abstract void Free(
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nuint index
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);
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public abstract SlabAllocationHandle<T> ReadAllocation();
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}
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public enum SlabBufferLayout
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{
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Sequential,
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Chunked
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}
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}
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