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Improved SegmentedPool with the introduction of handles and alignment (#1)

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Jim
2026-03-20 17:33:30 +00:00
parent dfbdf905fe
commit 8bf297a244
15 changed files with 2788 additions and 674 deletions
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28
UnmangedMMU/Allocators/DefaultUnmanagedAllocator.cs
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@@ -3,14 +3,36 @@
namespace UnmanagedMMU.Allocators
{
/// <summary>
/// Wrapper class around <see cref="NativeMemory.Alloc(nuint)"/> and <see cref="NativeMemory.Free(void*)"/>.
/// Wrapper class around <see cref="NativeMemory.AlignedAlloc(nuint, nuint)"/> and <see cref="NativeMemory.AlignedFree(void*)"/>.
/// </summary>
internal sealed unsafe class DefaultUnmanagedAllocator : IUnmanagedAllocator
{
/// <inheritdoc/>
public void* Alloc(nuint size) => NativeMemory.Alloc(size);
public void* Alloc(nuint size)
{
return NativeMemory.AlignedAlloc(size, 16);
}
/// <inheritdoc/>
public void Free(void* ptr) => NativeMemory.Free(ptr);
public void* AllocAligned(nuint size, nuint alignment)
{
if (!((alignment & (alignment - 1)) == 0 && alignment > 0))
{
throw new ArgumentException("Alignment must be a power of 2.", nameof(alignment));
}
return NativeMemory.AlignedAlloc(size, alignment);
}
/// <inheritdoc/>
public void Free(void* ptr)
{
NativeMemory.Free(ptr);
}
/// <inheritdoc/>
public void FreeAligned(void* ptr, nuint alignment = 0)
{
NativeMemory.AlignedFree(ptr);
}
}
}

24
UnmangedMMU/Allocators/IUnmanagedAllocator.cs
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@@ -1,9 +1,11 @@
namespace UnmanagedMMU.Allocators
using System.Runtime.InteropServices;
namespace UnmanagedMMU.Allocators
{
/// <summary>
/// Interface that defines an Unmanaged allocator
/// </summary>
internal unsafe interface IUnmanagedAllocator
public unsafe interface IUnmanagedAllocator
{
/// <summary>
/// Allocates an unmanaged memory block of the specified size.
@@ -14,10 +16,28 @@
/// </returns>
void* Alloc(nuint size);
/// <summary>
/// Allocates an unmanaged memory block of the specified size with the requested alignment
/// </summary>
/// <param name="size">The number of bytes to allocate.</param>
/// <param name="alignment">The alignment, in bytes, of the block to allocate. This must be a power of <c>2</c></param>
/// <returns></returns>
void* AllocAligned(nuint size, nuint alignment);
/// <summary>
/// Frees a previously allocated unmanaged memory block.
/// </summary>
/// <param name="ptr">A pointer to the beginning of the memory block to free.</param>
/// <remarks>This method should only be called on with pointers allocated with <see cref="Alloc"/>.</remarks>
void Free(void* ptr);
/// <summary>
/// Frees a previously allocated unmanaged aligned memory block
/// </summary>
/// <param name="ptr">A pointer to the beginning of the memory block to free.</param>
/// <param name="alignment">The alignment that the memory refered to by <paramref name="ptr"/> was aligned at (This parameter can be ignored if the underlying allocator does not need it)</param>
/// <remarks>This method should only be called on with pointers allocated with <see cref="AllocAligned"/>.</remarks>
void FreeAligned(void* ptr, nuint alignment = 0);
}
}

16
UnmangedMMU/Allocators/IUnmanagedMemoryOwner.cs Normal file
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@@ -0,0 +1,16 @@
using UnmanagedMMU.Handles.Internal;
namespace UnmanagedMMU.Allocators
{
/// <summary>
/// Interface that defines a mechanisim for the owner of an unmanaged memory allocation
/// </summary>
internal interface IUnmanagedMemoryOwner
{
/// <summary>
/// Frees the allocated memory represented by <paramref name="handle"/> back to the owning <see cref="IUnmanagedMemoryOwner"/> instance
/// </summary>
void Free(IOwnedHandle handle);
}
}

170
UnmangedMMU/Diagnostics/SegmentedPoolDiagnostics.cs Normal file
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@@ -0,0 +1,170 @@
using static UnmanagedMMU.SegmentedPool;
namespace UnmanagedMMU.Diagnostics
{
/// <summary>
/// Static helper class for generating diagnostics and suggestions for SegmentedPool.
/// Separates report generation logic from the pool implementation.
/// </summary>
public static class SegmentedPoolDiagnostics
{
/// <summary>
/// Generates a formatted report string including suggestions.
/// </summary>
public static string GenerateReport(PoolState state)
{
string status = state.BaseAligned ? "OK" : "FAIL";
string segmentStatus = $"{state.ActiveSegmentCount} active, {state.FreeSegmentCount} free";
double efficiency = (state.TotalUsed + state.PaddingBytes) > 0
? (100.0 * state.TotalUsed / (state.TotalUsed + state.PaddingBytes))
: 100.0;
string efficiencyLabel = GetEfficiencyLabel(efficiency, state.SegmentAlignment);
string suggestionLine = state.Suggestion;
if (!string.IsNullOrEmpty(suggestionLine))
{
suggestionLine = $"\n {suggestionLine}";
}
return $"=== SegmentedPool Diagnostics ===\n" +
$" Configuration\n" +
$" Segment Alignment: {state.SegmentAlignment} bytes (Min Base Alignment)\n" +
$" Segment Size: {FormatBytes(state.SegmentSize)}\n" +
$" Segment Summary\n" +
$" Total Segments: {state.TotalSegmentCount} ({segmentStatus})\n" +
$" Potential Savings: {FormatBytes(state.PotentialSavings)} (via Trim())\n" +
$" Current Segment\n" +
$" Base Address: 0x{(nuint)state.CurrentBase:x}\n" +
$" Offset: {state.CurrentOffset} bytes\n" +
$" Base Alignment: {status} (To {state.SegmentAlignment} bytes)\n" +
$" Memory Statistics\n" +
$" Total Reserved: {FormatBytes(state.TotalReserved)}\n" +
$" Total Used: {FormatBytes(state.TotalUsed)}\n" +
$" Efficiency: {efficiency:F0}% ({efficiencyLabel})\n" +
$" Padding Overhead: {FormatBytes(state.PaddingBytes)}\n" +
$" Allocation Breakdown\n" +
$" Data Bytes: {FormatBytes(state.TotalUsed)}\n" +
$" Alignment Padding: {FormatBytes(state.PaddingBytes)}\n" +
$" Total Segment Space: {FormatBytes(state.CurrentOffset)}\n" +
$" Action Required:{suggestionLine}";
}
private static string GetEfficiencyLabel(double efficiency, nuint segmentAlignment)
{
int threshold = segmentAlignment switch
{
8 => 50,
16 => 60,
32 => 75,
64 => 85,
_ => 90
};
if (efficiency >= 100) return "Perfect";
if (efficiency >= threshold) return "Good";
return "High Overhead";
}
private static string FormatBytes(nuint bytes)
{
if (bytes >= 1073741824) return $"{bytes / 1073741824} GiB";
if (bytes >= 1048576) return $"{bytes / 1048576} MiB";
if (bytes >= 1024) return $"{bytes / 1024} KiB";
return $"{bytes} B";
}
/// <summary>
/// Generates actionable suggestions based on pool metrics.
/// Comprehensive coverage of all pool states.
/// </summary>
public static string GenerateSuggestions(PoolState state, DiagnosticConfig config)
{
// === CRITICAL ISSUES ===
// 1. Base alignment broken (should never happen)
if (!state.BaseAligned)
{
return "CRITICAL: Segment base not aligned to configured boundary. This indicates a memory management bug.";
}
// === HIGH PRIORITY ===
// 2. Pool exhausted (Next alloc blocks)
if (state.FreeSegmentCount == 0)
{
return "INFO: No free segments available. Next allocation will block. Call Reset() to recycle segments or increase initialSegments.";
}
// 3. Significant Memory Waste (Trim Opportunity)
if (state.PotentialSavings > 0)
{
double wasteRatio = (double)state.PotentialSavings / state.TotalReserved;
if (wasteRatio > 0.50)
{
return $"ACTION: {state.FreeSegmentCount - 16} excess segments can be freed. Calling Trim() will recover {FormatBytes(state.PotentialSavings)} ({(wasteRatio * 100):F0}% of reserved memory).";
}
if (state.PotentialSavings > 1024 * 1024)
{
return $"ACTION: Excess free segments ({state.FreeSegmentCount}). Calling Trim() will recover {FormatBytes(state.PotentialSavings)}. Current usage: {FormatBytes(state.TotalUsed)} of {FormatBytes(state.TotalReserved)}. Efficiency: {(state.TotalUsed / state.TotalReserved) * 100:F0}%.";
}
}
// 4. Efficiency Issues (Alignment Mismatch)
double efficiency = (state.TotalUsed + state.PaddingBytes) > 0
? (100.0 * state.TotalUsed / (state.TotalUsed + state.PaddingBytes))
: 100.0;
int threshold = state.SegmentAlignment switch
{
8 => 50,
16 => 60,
32 => 75,
64 => 85,
_ => 90
};
if (efficiency < threshold)
{
if (state.SegmentAlignment <= 32)
{
return $"Suggestion: Current alignment ({state.SegmentAlignment}B) is low. Increase to 32B for better efficiency.";
}
else
{
return $"Suggestion: Verify allocation alignment matches segment base ({state.SegmentAlignment}B). Efficiency is {efficiency:F0}%.";
}
}
// 5. Segment Nearly Full
if (config.SegmentSize > 0 && state.CurrentOffset > config.SegmentSize * 0.90)
{
return "INFO: Current segment nearly full. Consider Reset() to reuse this segment instead of allocating a new one.";
}
// === LOW PRIORITY / OPTIONAL ===
// 6. Low Utilization (Memory Bloat)
if (state.TotalReserved > 16 * 1024 * 1024)
{
double usageRatio = (double)state.TotalUsed / state.TotalReserved;
if (usageRatio < 0.10)
{
return $"INFO: Low memory utilization ({usageRatio:P0}). Consider Reset() or Trim() to reduce footprint.";
}
}
return "Pool operating normally.";
}
}
/// <summary>
/// Configuration details passed to diagnostics for context-aware suggestions.
/// </summary>
public readonly struct DiagnosticConfig
{
public nuint SegmentSize { get; init; }
public nuint TotalReserved { get; init; }
}
}

27
UnmangedMMU/Handles/IMemoryHandle.cs Normal file
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@@ -0,0 +1,27 @@
using UnmanagedMMU.Allocators;
namespace UnmanagedMMU.Handles
{
/// <summary>
/// Interface that represents an untyped handle to unmanaged memory.
/// </summary>
public unsafe interface IMemoryHandle
{
/// <summary>
/// Gets the raw pointer to the underlying unmanaged memory block.
/// </summary>
/// <remarks>
/// The returned pointer is valid only for the lifetime of the allocator
/// that created this <see cref="IMemoryHandle"/>.
/// </remarks>
void* Pointer { get; }
/// <summary>
/// Gets the number of bytes in the unmanaged memory block
/// represented by this <see cref="IMemoryHandle"/>.
/// </summary>
nuint ByteCount { get; }
}
}

34
UnmangedMMU/Handles/IMemoryHandleT.cs Normal file
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@@ -0,0 +1,34 @@
using UnmanagedMMU.Allocators;
namespace UnmanagedMMU.Handles
{
/// <summary>
/// Interface that represents a typed handle to unmanaged memory.
/// </summary>
/// <typeparam name="T">
/// The unmanaged element type stored in the underlying memory block.
/// </typeparam>
public unsafe interface IMemoryHandle<T> : IMemoryHandle, IDisposable where T : unmanaged
{
/// <summary>
/// Gets the typed <typeparamref name="T"/> pointer to the underlying unmanaged memory block.
/// </summary>
/// <remarks>
/// The pointer becomes invalid after the handle is disposed.
/// </remarks>
new T* Pointer { get; }
/// <summary>
/// Gets the number of elements contained in this handle.
/// </summary>
nuint Length { get; }
/// <summary>
/// Returns the underlying unmanaged memory block held by this handle back to the owning <see cref="IUnmanagedMemoryOwner"/> instance
/// </summary>
new void Dispose() { }
}
}

15
UnmangedMMU/Handles/Internal/IOwnedHandle.cs Normal file
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@@ -0,0 +1,15 @@
using UnmanagedMMU.Allocators;
namespace UnmanagedMMU.Handles.Internal
{
/// <summary>
/// Interface defining an interface for handle ownership semantics
/// </summary>
internal interface IOwnedHandle: IMemoryHandle
{
/// <summary>
/// Returns the <see cref="IUnmanagedMemoryOwner"/> that created owns this <see cref="IOwnedHandle"/>
/// </summary>
IUnmanagedMemoryOwner GetOwner();
}
}

126
UnmangedMMU/Handles/MemoryHandleBase.cs Normal file
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@@ -0,0 +1,126 @@
using System.Diagnostics;
using UnmanagedMMU.Allocators;
using UnmanagedMMU.Handles.Internal;
namespace UnmanagedMMU.Handles
{
/// <summary>
/// Provides a base implementation for typed unmanaged memory handles.
/// </summary>
/// <typeparam name="T">
/// The unmanaged element type stored in the underlying memory block.
/// </typeparam>
/// <remarks>
/// This class encapsulates the raw pointer and byte length of an unmanaged
/// memory allocation and provides typed access to that memory.
///
/// Memory lifetime is controlled by the originating allocator; this type
/// does not own or free the underlying memory.
/// </remarks>
internal unsafe abstract class MemoryHandleBase<T> : IMemoryHandle<T>, IOwnedHandle where T : unmanaged
{
/// <summary>
/// The <see cref="IUnmanagedMemoryOwner"/> that owns this <see cref="MemoryHandleBase{T}"/> handle
/// </summary>
private readonly IUnmanagedMemoryOwner _owner;
/// <summary>
/// The raw pointer to the unmanaged memory block
/// </summary>
private readonly void* _ptr;
/// <summary>
/// The size of the unmanaged memory block in bytes
/// </summary>
private readonly nuint _bytelen;
/// <summary>
/// Indicates whether this <see cref="MemoryHandleBase{T}"/> has been disposed.
/// </summary>
private bool _disposed;
/// <summary>
/// Initializes a new <see cref="MemoryHandleBase{T}"/> instnace
/// </summary>
/// <param name="ptr">Pointer to the allocated unmanaged memory</param>
/// <param name="byteLength">The size of the unallocated memory block in bytes</param>
/// <param name="owner">The <see cref="IUnmanagedMemoryOwner"/> that owns the <see cref="MemoryHandleBase{T}"/> handle being created</param>
protected MemoryHandleBase(void* ptr, nuint byteLength, IUnmanagedMemoryOwner owner)
{
// Defensive check
Debug.Assert(ptr != null, message: "BUG CHECK: E_INVALID_MEMORY_HANDLE");
_ptr = ptr;
_bytelen = byteLength;
_owner = owner;
}
/// <summary>
/// Gets the raw pointer to the unmanaged memory block
/// </summary>
public virtual void* Pointer
{
get { return _ptr; }
}
/// <summary>
/// Gets the typed pointer to the unmanged memory block
/// </summary>
T* IMemoryHandle<T>.Pointer
{
get { return (T*)_ptr; }
}
/// <summary>
/// Gets the size in bytes of the unmanaged memory block
/// </summary>
public nuint ByteCount
{
get { return _bytelen; }
}
/// <summary>
/// Gets the number of elements of type <typeparamref name="T"/>
/// contained in the unmanaged memory block.
/// </summary>
public nuint Length
{
get { return _bytelen / (nuint)sizeof(T); }
}
/// <summary>
/// Releases the unmanaged resources held by the <see cref="MemoryHandleBase{T}"/>.
/// </summary>
/// <remarks>
/// This method is idempotent and safe to call multiple times. It ensures the underlying
/// memory is cleaned up according to the implementation in <see cref="OnDispose()"/>.
/// After disposal, the handle is invalid for further use.
/// </remarks>
public void Dispose()
{
if (_disposed)
{
return;
}
_disposed = true;
OnDispose();
GC.SuppressFinalize(this);
}
/// <summary>
/// Override in derived classes to define lifecycle behavior.
/// This is an abstract method to ensure cleanup logic is always implemented.
/// </summary>
protected abstract void OnDispose();
/// <summary>
/// Returns the <see cref="IUnmanagedMemoryOwner"/> that created owns this <see cref="MemoryHandleBase{T}"/> instance
/// </summary>
/// <returns>The <see cref="IUnmanagedMemoryOwner"/> that created owns this <see cref="MemoryHandleBase{T}"/> instance</returns>
public IUnmanagedMemoryOwner GetOwner()
{
return _owner;
}
}
}

21
UnmangedMMU/Handles/PersistentMemoryHandle.cs Normal file
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@@ -0,0 +1,21 @@
using UnmanagedMMU.Allocators;
namespace UnmanagedMMU.Handles
{
internal sealed unsafe class PersistentMemoryHandle<T> : MemoryHandleBase<T> where T : unmanaged
{
public PersistentMemoryHandle(void* ptr, nuint byteLength, IUnmanagedMemoryOwner owner) : base(ptr, byteLength, owner)
{
}
protected override void OnDispose()
{
if (Pointer != null)
{
GetOwner().Free(this);
// No need to set _ptr = null here; MemoryHandleBase._disposed flag prevents double-free
}
}
}
}

21
UnmangedMMU/Handles/SegmentedMemoryHandle.cs Normal file
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@@ -0,0 +1,21 @@
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using UnmanagedMMU.Allocators;
namespace UnmanagedMMU.Handles
{
internal sealed unsafe class SegmentedMemoryHandle<T> : MemoryHandleBase<T> where T : unmanaged
{
public SegmentedMemoryHandle(void* ptr, nuint byteLength, IUnmanagedMemoryOwner owner) : base(ptr, byteLength, owner)
{
}
protected override void OnDispose()
{
return;
}
}
}

692
UnmangedMMU/SegmentedPool.cs
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@@ -2,9 +2,50 @@
{
using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;
using System.Threading;
using UnmanagedMMU.Allocators;
using UnmanagedMMU.Diagnostics;
using UnmanagedMMU.Handles;
using UnmanagedMMU.Handles.Internal;
/// <summary>
/// Represents configurable alignment requirements for memory segments and allocations.
/// Values are powers of 2 and reflect common hardware requirements (SIMD, cache lines, native pointer size).
/// </summary>
public enum SegmentAlignment
{
/// <summary>
/// 8-byte alignment. Minimum for 64-bit pointers and primitives (long, double).
/// </summary>
Aligned8 = 8,
/// <summary>
/// 16-byte alignment. Required for Vector128 (SSE/NEON).
/// Common default for general-purpose SIMD workloads.
/// </summary>
Aligned16 = 16,
/// <summary>
/// 32-byte alignment. Required for Vector256 (AVX).
/// Recommended default for SIMD-heavy applications.
/// </summary>
Aligned32 = 32,
/// <summary>
/// 64-byte alignment. Matches standard CPU cache-line size.
/// Ensures segment bases align to cache line boundaries, minimizing cache-line splits.
/// </summary>
Aligned64 = 64,
/// <summary>
/// 128-byte alignment.
/// Advanced optimization for specific cache-aware algorithms or AVX-512 contexts.
/// </summary>
Aligned128 = 128
}
/// <summary>
/// Implementation of segmented Bump-Allocator.
@@ -13,7 +54,7 @@
/// This ensures allocations are fast and contiguous within a segment.
/// Once a segment is full, a new one is automatically allocated
/// </summary>
public unsafe sealed class SegmentedPool : IDisposable
public unsafe sealed class SegmentedPool : IDisposable, IUnmanagedMemoryOwner
{
/// <summary>
/// The default size for a <see cref="Segment"/>
@@ -25,6 +66,11 @@
/// </summary>
private nuint _currentSegmentSize;
/// <summary>
/// The alignment that each new <see cref="Segment"/> should be on
/// </summary>
private readonly nuint _segmentAlignment;
/// <summary>
/// Queue of free segments
/// </summary>
@@ -36,12 +82,12 @@
private readonly List<IntPtr> _activeSegments = [];
/// <summary>
/// Tracks the total amount of allocated bytes
/// Tracks the total bytes of memory reserved from the provided <see cref="IUnmanagedAllocator"/>
/// </summary>
private nuint _totalAllocated = 0;
private nuint _totalReserved = 0;
/// <summary>
/// Tracks the total amount of allocated bytes current in use
/// Tracks the total amount of allocated bytes currently in use
/// </summary>
private nuint _totalUsed = 0;
@@ -51,7 +97,7 @@
private readonly Lock _lock = new();
/// <summary>
/// Indicates whether the <see cref="SegmentedPool"/> has been disposed.
/// Indicates whether this <see cref="SegmentedPool"/> has been disposed.
/// </summary>
private volatile bool _disposed;
@@ -60,8 +106,16 @@
/// </summary>
private Segment* _current;
/// <summary>
/// Allocator interface used for all underlying unmanaged memory operations.
/// </summary>
private readonly IUnmanagedAllocator _allocator;
/// <summary>
/// Indicates if allocations from the pool should be zeroed.
/// </summary>
private readonly bool _zeroMemory;
/// <summary>
/// Represents a memory segment in the <see cref="SegmentedPool"/>.
/// </summary>
@@ -93,16 +147,152 @@
}
/// <summary>
/// Readonly snapshot of the current pool state for diagnostics.
/// </summary>
public readonly struct PoolState
{
/// <summary>
/// The configured segment alignment setting for this pool instance.
/// This is the MINIMUM alignment requirement for the segment base.
/// </summary>
public nuint SegmentAlignment { get; init; }
/// <summary>
/// The size, in bytes, of each segment allocated by the pool.
/// </summary>
public nuint SegmentSize { get; init; }
/// <summary>
/// Total bytes currently reserved from the system.
/// </summary>
public nuint TotalReserved { get; init; }
/// <summary>
/// Total bytes currently used by allocations.
/// </summary>
public nuint TotalUsed { get; init; }
/// <summary>
/// Current active segment base address.
/// </summary>
public nuint CurrentBase { get; init; }
/// <summary>
/// Current offset within the segment.
/// </summary>
public nuint CurrentOffset { get; init; }
/// <summary>
/// Checks if the current segment base is aligned to the configured <see cref="SegmentAlignment"/> setting.
/// </summary>
public bool BaseAligned { get; init; }
/// <summary>
/// Number of active segments currently being used.
/// </summary>
public int ActiveSegmentCount { get; init; }
/// <summary>
/// Number of recycled segments available for reuse.
/// </summary>
public int FreeSegmentCount { get; init; }
/// <summary>
/// Total number of segments in the pool (Active + Free).
/// </summary>
public int TotalSegmentCount { get; init; }
/// <summary>
/// Bytes lost to alignment padding vs actual data in current segment.
/// Computed as: CurrentOffset - TotalUsedBytes.
/// </summary>
public nuint PaddingBytes { get; init; }
/// <summary>
/// Memory that could be freed if Trim() is called with default args (minFreeSegments: 16).
/// </summary>
public nuint PotentialSavings { get; init; }
public string Suggestion { get; init; }
}
/// <summary>
/// Readonly snapshot of a specific segment.
/// </summary>
public readonly struct SegmentInfo
{
/// <summary>
/// Segment index within the active list.
/// </summary>
public int Index { get; init; }
/// <summary>
/// Base address of the segment (actual unmanaged memory pointer).
/// </summary>
public nuint BaseAddress { get; init; }
/// <summary>
/// Current offset usage (bytes used since segment reset).
/// </summary>
public nuint UsedBytes { get; init; }
/// <summary>
/// Total capacity of the segment.
/// </summary>
public nuint Size { get; init; }
/// <summary>
/// Indicates if this is the currently active segment.
/// </summary>
public bool IsActive { get; init; }
/// <summary>
/// The alignment requirement for the segment base itself.
/// </summary>
public nuint AlignmentRequirement { get; init; }
/// <summary>
/// True if <see cref="BaseAddress"/> is a multiple of <see cref="AlignmentRequirement"/>.
/// </summary>
public bool IsAligned { get; init; }
public override string ToString()
{
bool aligned = IsAligned;
string status = IsActive ? "CURRENT" : "INACTIVE";
double usagePercent = Size > 0 ? ((double)UsedBytes / Size) * 100 : 0;
string alignStatus = aligned ? "Aligned" : "Misaligned";
return $" Segment #{Index} [{status}]\n" +
$" Base Address: 0x{(nuint)BaseAddress:x}\n" +
$" Size: {FormatBytes(Size)}\n" +
$" Used: {FormatBytes(UsedBytes)} ({usagePercent:F2}%)\n" +
$" Base Alignment: {AlignmentRequirement} bytes - {alignStatus}";
}
private static string FormatBytes(nuint bytes)
{
if (bytes >= 1073741824) return $"{bytes / 1073741824} GiB";
if (bytes >= 1048576) return $"{bytes / 1048576} MiB";
if (bytes >= 1024) return $"{bytes / 1024} KiB";
return $"{bytes} B";
}
}
/// <summary>
/// Initializes a new <see cref="SegmentedPool"/> with the specified default <paramref name="segmentSize"/> and <paramref name="initialSegments"/> count
/// </summary>
/// <param name="segmentSize">Size of each segment in bytes (default 4 MiB)</param>
/// <param name="segmentAlignment">Alignment requirement for each allocated segment and . Must be a power of 2 (Default 32)</param>
/// <param name="initialSegments">Number of segments to pre-allocate to the pool</param>
/// <param name="zeroMemory">When true, memory returned from the pool is zero-initialized.
/// When false, memory may contain previously used data and it is the caller's responsibility to clear it if required.</param>
/// <exception cref="ArgumentException">
/// Thrown if <paramref name="segmentSize"/> is zero, or if <paramref name="initialSegments"/> is less than 1.
/// </exception>
public SegmentedPool(nuint segmentSize = _defaultSegmentSize, int initialSegments = 4)
: this(segmentSize, initialSegments, new DefaultUnmanagedAllocator())
public SegmentedPool(nuint segmentSize = _defaultSegmentSize, SegmentAlignment segmentAlignment = SegmentAlignment.Aligned32, int initialSegments = 4, bool zeroMemory = false)
: this(segmentSize, segmentAlignment, initialSegments, zeroMemory, new DefaultUnmanagedAllocator())
{
}
@@ -110,28 +300,30 @@
/// Initializes a new <see cref="SegmentedPool"/> with the specified default <paramref name="segmentSize"/> and <paramref name="initialSegments"/> count
/// </summary>
/// <param name="segmentSize">Size of each segment in bytes (default 4 MiB)</param>
/// <param name="segmentAlignment">Alignment requirement for each allocated segment. Must be a power of 2 (Default 32)</param>
/// <param name="initialSegments">Number of segments to pre-allocate to the pool</param>
/// <param name="zeroMemory">When true, memory returned from the pool is zero-initialized.
/// When false, memory may contain previously used data and it is the caller's responsibility to clear it if required.</param>
/// <param name="allocator">IUnmanagedAllocator instance that implements the allocator</param>
/// <exception cref="ArgumentException">
/// Thrown if <paramref name="segmentSize"/> is zero, or if <paramref name="initialSegments"/> is less than 1.
/// </exception>
internal SegmentedPool(nuint segmentSize, int initialSegments, IUnmanagedAllocator allocator)
internal SegmentedPool(nuint segmentSize, SegmentAlignment segmentAlignment, int initialSegments, bool zeroMemory, IUnmanagedAllocator allocator)
{
if (segmentSize == 0)
{
throw new ArgumentException("Segment size must be greater than zero.", nameof(segmentSize));
}
if (initialSegments < 1)
{
throw new ArgumentException("Initial segments count must be at least 1.", nameof(initialSegments));
}
ArgumentOutOfRangeException.ThrowIfNegativeOrZero(segmentSize);
ArgumentOutOfRangeException.ThrowIfLessThan(initialSegments, 1);
_allocator = allocator;
_currentSegmentSize = segmentSize;
_segmentAlignment = (nuint)segmentAlignment;
_zeroMemory = zeroMemory;
Segment* seg;
// Pre-allocate segments
for (int i = 0; i < initialSegments; i++)
{
_freeSegments.Push((IntPtr)AllocateNewSegment(_currentSegmentSize));
seg = AllocateNewSegment(_currentSegmentSize);
ZeroSegment(seg);
_freeSegments.Push((IntPtr)seg);
}
@@ -145,7 +337,13 @@
/// <returns>The number of free segments.</returns>
public int FreeSegmentCount
{
get { return _freeSegments.Count; }
get
{
lock (_lock)
{
return _freeSegments.Count;
}
}
}
/// <summary>
@@ -154,7 +352,13 @@
/// <returns>The number of currently active Segments.</returns>
public int ActiveSegmentCount
{
get { return _activeSegments.Count; }
get
{
lock (_lock)
{
return _activeSegments.Count;
}
}
}
/// <summary>
@@ -163,7 +367,13 @@
/// <returns>The total number of bytes that have been allocated.</returns>
public nuint TotalAllocatedBytes
{
get { return _totalAllocated; }
get
{
lock (_lock)
{
return _totalReserved;
}
}
}
/// <summary>
@@ -172,7 +382,13 @@
/// <returns>The total number of bytes that are in use.</returns>
public nuint TotalUsedBytes
{
get { return _totalUsed; }
get
{
lock (_lock)
{
return _totalUsed;
}
}
}
/// <summary>
@@ -198,6 +414,153 @@
get { return _disposed; }
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static nuint AlignUp(nuint value, nuint alignment)
{
return (value + alignment - 1) & ~(alignment - 1);
}
/// <summary>
/// Zeroes the memory <see cref="Segment"></see> if the <see cref="SegmentedPool"/> is configured to do so.
/// Called whenever a segment becomes active for use (new or reused).
/// </summary>
/// <param name="segment">Pointer to the Segment struct to initialize.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private void ZeroSegment(Segment* segment)
{
if (_zeroMemory)
{
Unsafe.InitBlockUnaligned(segment->Ptr, 0, (uint)segment->Size);
}
}
/// <summary>
/// Allocates a block of unmanaged memory of size <paramref name="count"/> for elements of type <typeparamref name="T"/> and returns a pointer to the allocated memory.
/// </summary>
/// <typeparam name="T">The unmanaged value type to store in the allocated memory. Must be a struct or primitive type.</typeparam>
/// <param name="count">The number of elements of type <typeparamref name="T"/> to allocate.</param>
/// <returns>A <typeparamref name="T"/> pointer to the first element of the allocated unmanaged memory block. The memory is valid until the <see cref="SegmentedPool"/> is reset or disposed.</returns>
/// <remarks>
/// <list type="bullet">
/// <item><description>This allocation is performed in unmanaged memory and bypasses the .NET garbage collector.</description></item>
/// <item><description>Accessing the memory after <see cref="Reset"/> or <see cref="Dispose"/> has been called is undefined behavior and may lead to crashes.</description></item>
/// </list>
/// </remarks>
/// <exception cref="ArgumentOutOfRangeException">
/// Thrown if <paramref name="count"/> is less than or equal to zero.
/// </exception>
/// <exception cref="OverflowException">
/// Thrown if the total allocation size (count * sizeof(T)) exceeds the maximum allowable size.
/// </exception>
private T* Alloc<T>(int count) where T : unmanaged
{
ArgumentOutOfRangeException.ThrowIfNegativeOrZero(count);
if ((nuint)count > nuint.MaxValue / (nuint)(sizeof(T)))
{
throw new OverflowException($"Requested allocation of {count} elements of type {typeof(T)} exceeds allowable maximum memory size.");
}
nuint bytes = (nuint)(count * sizeof(T));
nuint alignment = _segmentAlignment > (nuint)sizeof(T) ? _segmentAlignment : (nuint)sizeof(T);
lock (_lock)
{
ThrowIfDisposed();
nuint currentPtr = (nuint)_current->Ptr + _current->Offset;
nuint alignedPtr = AlignUp(currentPtr, alignment);
nuint alignedOffset = alignedPtr - (nuint)_current->Ptr;
// Check space INCLUDING padding
if (alignedOffset + bytes > _current->Size)
{
SwitchSegment(bytes);
// Recalcuate from new the base of the new segment
currentPtr = (nuint)_current->Ptr;
alignedPtr = AlignUp(currentPtr, alignment);
alignedOffset = alignedPtr - (nuint)_current->Ptr;
}
T* ptr = (T*)(_current->Ptr + alignedOffset);
_current->Offset = alignedOffset + bytes;
_totalUsed += bytes;
return ptr;
}
}
private T* AllocateWithAlignment<T>(int count, nuint alignment) where T : unmanaged
{
ArgumentOutOfRangeException.ThrowIfNegativeOrZero(count);
if ((nuint)count > nuint.MaxValue / (nuint)(sizeof(T)))
{
throw new OverflowException($"Requested allocation of {count} elements of type {typeof(T)} exceeds allowable maximum memory size.");
}
nuint bytes = (nuint)(count * sizeof(T));
lock (_lock)
{
ThrowIfDisposed();
nuint currentPtr = (nuint)_current->Ptr + _current->Offset;
nuint alignedPtr = AlignUp(currentPtr, alignment);
nuint alignedOffset = alignedPtr - (nuint)_current->Ptr;
if (alignedOffset + bytes > _current->Size)
{
SwitchSegment(bytes);
currentPtr = (nuint)_current->Ptr;
alignedPtr = AlignUp(currentPtr, alignment);
alignedOffset = alignedPtr - (nuint)_current->Ptr;
}
T* ptr = (T*)(_current->Ptr + alignedOffset);
_current->Offset = alignedOffset + bytes;
_totalUsed += bytes;
return ptr;
}
}
/// <summary>
/// Switches to a new <see cref="Segment"/> when the current <see cref="Segment"/> is full.
/// </summary>
/// <param name="requiredBytes">The number of bytes required for the upcoming allocation. If the current <see cref="Segment"/> does not have enough free space, a new <see cref="Segment"/> will be used.</param>
private void SwitchSegment(nuint requiredBytes)
{
Segment* segment;
// Allocate fresh Segment if needed
if (_freeSegments.Count == 0 || requiredBytes > _currentSegmentSize)
{
segment = AllocateNewSegment(requiredBytes > _currentSegmentSize ? requiredBytes : _currentSegmentSize);
}
else
{
segment = (Segment*)_freeSegments.Pop();
segment->Offset = 0;
}
ZeroSegment(segment);
_activeSegments.Add((IntPtr)segment);
_current = segment;
}
/// <summary>
/// Allocates a new <see cref="Segment"/>
/// </summary>
/// <param name="size"> Size, in bytes, for the new <see cref="Segment"/>. </param>
/// <returns>A pointer to the newly allocated <see cref="Segment"/></returns>
private Segment* AllocateNewSegment(nuint size)
{
byte* ptr = (byte*)_allocator.AllocAligned(size, _segmentAlignment);
// Allocate metadata struct with its natural alignment (8 bytes for 64-bit nuint)
Segment* segment = (Segment*)_allocator.AllocAligned((nuint)sizeof(Segment), 8);
segment->Ptr = ptr;
segment->Offset = 0;
segment->Size = size;
_totalReserved += size;
return segment;
}
/// <summary>
/// Sets the current <see cref="Segment"/> size used for subsequent allocations.
/// </summary>
@@ -236,15 +599,15 @@
}
/// <summary>
/// Allocates a span of unmanaged memory of size <paramref name="count"/> for elements of type <typeparamref name="T"/>.
/// Allocates a block of unmanaged memory of size <paramref name="count"/> for elements of type <typeparamref name="T"/> and returns a handle representing the allocation.
/// </summary>
/// <typeparam name="T">The unmanaged value type to store in the allocated memory. Must be a struct or primitive type.</typeparam>
/// <param name="count">The number of elements of type <typeparamref name="T"/> to allocate.</param>
/// <returns>A <see cref="Span{T}"/> representing the allocated memory. The span is valid until the <see cref="SegmentedPool"/> is reset or disposed.</returns>
/// <returns>A <see cref="IMemoryHandle{T}"/> representing the allocated memory. The handle is valid until either <see cref="Reset"/> or <see cref="Dispose"/> is called on this <see cref="SegmentedPool"/>.</returns>
/// <remarks>
/// <list type="bullet">
/// <item><description>This allocation is performed in unmanaged memory and bypasses the .NET garbage collector.</description></item>
/// <item><description>Accessing the memory after <see cref="Reset"/> or <see cref="Dispose"/> has been called is undefined behavior and may lead to crashes.</description></item>
/// <item><description>Accessing the memory after <see cref="Reset"/> or <see cref="Dispose"/> has been called is undefined behavior.</description></item>
/// </list>
/// </remarks>
/// <exception cref="ArgumentOutOfRangeException">
@@ -253,73 +616,43 @@
/// <exception cref="OverflowException">
/// Thrown if the total allocation size (count * sizeof(T)) exceeds the maximum allowable size.
/// </exception>
public Span<T> Allocate<T>(int count) where T : unmanaged
public IMemoryHandle<T> Allocate<T>(int count) where T : unmanaged
{
ThrowIfDisposed();
if (count <= 0)
{
throw new ArgumentOutOfRangeException(nameof(count), "Allocation count must be greater than zero.");
}
if ((nuint)count > nuint.MaxValue / (nuint)(sizeof(T)))
{
throw new OverflowException($"Requested allocation of {count} elements of type {typeof(T)} exceeds allowable maximum memory size.");
}
nuint bytes = (nuint)(count * sizeof(T));
lock (_lock)
{
// Enough space in current segment?
if (_current->Offset + bytes > _current->Size)
SwitchSegment(bytes);
T* ptr = (T*)(_current->Ptr + _current->Offset);
_current->Offset += bytes;
_totalUsed += bytes;
return new Span<T>(ptr, count);
}
T* ptr = Alloc<T>(count);
nuint byteLength = (nuint)count * (nuint)sizeof(T);
return new SegmentedMemoryHandle<T>(ptr, byteLength, this);
}
/// <summary>
/// Switches to a new <see cref="Segment"/> when the current <see cref="Segment"/> is full.
/// Allocates a block of unmanaged memory of size <paramref name="count"/> for elements of type <typeparamref name="T"/> with the specified <paramref name="alignment"/> and returns a handle representing the allocation.
/// </summary>
/// <param name="requiredBytes">The number of bytes required for the upcoming allocation. If the current <see cref="Segment"/> does not have enough free space, a new <see cref="Segment"/> will be used.</param>
private void SwitchSegment(nuint requiredBytes)
/// <typeparam name="T">The unmanaged value type to store in the allocated memory. Must be a struct or primitive type.</typeparam>
/// <param name="count">The number of elements of type <typeparamref name="T"/> to allocate.</param>
/// <param name="alignment">The alignment to aliign the allocation to inside of the currently active <see cref="Segment"/></param>
/// <returns>A <see cref="IMemoryHandle{T}"/> representing the allocated memory. The handle is valid until either <see cref="Reset"/> or <see cref="Dispose"/> is called on this <see cref="SegmentedPool"/>.</returns>
/// <remarks>
/// <list type="bullet">
/// <item><description>This allocation is performed in unmanaged memory and bypasses the .NET garbage collector.</description></item>
/// <item><description>Accessing the memory after <see cref="Reset"/> or <see cref="Dispose"/> has been called is undefined behavior.</description></item>
/// </list>
/// </remarks>
/// <exception cref="ArgumentOutOfRangeException">
/// Thrown if <paramref name="count"/> is less than or equal to zero.
/// </exception>
/// <exception cref="OverflowException">
/// Thrown if the total allocation size (count * sizeof(T)) exceeds the maximum allowable size.
/// </exception>
public IMemoryHandle<T> AllocateAligned<T>(int count, SegmentAlignment alignment) where T : unmanaged
{
Segment* segment;
nuint requestedAlignment = (nuint)alignment;
nuint typeSize = (nuint)sizeof(T);
// Ensure alignment is at least the size of T (never under-align for types)
nuint effectiveAlignment = requestedAlignment < typeSize ? typeSize : requestedAlignment;
// Allocate fresh Segment if needed
if (_freeSegments.Count == 0 || requiredBytes > _currentSegmentSize)
{
segment = AllocateNewSegment(requiredBytes > _currentSegmentSize ? requiredBytes : _currentSegmentSize);
}
else
{
segment = (Segment*)_freeSegments.Pop();
segment->Offset = 0;
}
T* ptr = AllocateWithAlignment<T>(count, effectiveAlignment);
nuint byteLength = (nuint)count * (nuint)sizeof(T);
return new SegmentedMemoryHandle<T>(ptr, byteLength, this);
_activeSegments.Add((IntPtr)segment);
_current = segment;
}
/// <summary>
/// Allocates a new <see cref="Segment"/>
/// </summary>
/// <param name="size">
/// Optional size, in bytes, for the new <see cref="Segment"/>.
/// If <c>null</c>, the default <see cref="Segment"/> size (<see cref="_defaultSegmentSize"/>) is used.
/// </param>
/// <returns>A pointer to the newly allocated <see cref="Segment"/></returns>
private Segment* AllocateNewSegment(nuint size)
{
byte* ptr = (byte*)_allocator.Alloc(size);
Segment* segment = (Segment*)_allocator.Alloc((nuint)sizeof(Segment));
segment->Ptr = ptr;
segment->Offset = 0;
segment->Size = size;
_totalAllocated += size;
return segment;
}
/// <summary>
@@ -344,9 +677,9 @@
Segment* segment = (Segment*)ip;
// Free the unmanaged memory
_allocator.Free(segment->Ptr);
_totalAllocated -= segment->Size;
_allocator.Free(segment);
_allocator.FreeAligned(segment->Ptr, _segmentAlignment);
_totalReserved -= segment->Size;
_allocator.FreeAligned(segment, 8);
}
}
}
@@ -365,6 +698,9 @@
Segment* segment = (Segment*)ip;
segment->Offset = 0;
_freeSegments.Push(ip);
// Zero memory if requested
ZeroSegment(segment);
}
_activeSegments.Clear();
@@ -380,7 +716,10 @@
// This should not be hit in normal circumstances as we always have _current
_current = AllocateNewSegment(_currentSegmentSize);
_activeSegments.Add((IntPtr)_current);
// Zero newly allocated segment if requested
ZeroSegment(_current);
}
// Optionally trim excess free segments after reset
if (trim)
{
@@ -389,6 +728,27 @@
}
}
/// <summary>
/// Frees <paramref name="handle"/>
/// </summary>
/// <param name="handle"></param>
/// <exception cref="NotImplementedException"></exception>
void IUnmanagedMemoryOwner.Free(IOwnedHandle handle)
{
ThrowIfDisposed();
if (handle.Pointer == null)
{
return;
}
if (handle.GetOwner() != this)
{
throw new InvalidOperationException(
"Attempted to free a handle from a different allocator pool.");
}
//
}
/// <summary>
/// Releases all unmanaged memory allocated by the <see cref="SegmentedPool"/> and clears internal state.
/// After calling this method, the pool can no longer be used for allocations.
@@ -406,26 +766,26 @@
return;
}
// Free active pages
// Free active segments
foreach (var ip in _activeSegments)
{
Segment* segment = (Segment*)ip;
_allocator.Free(segment->Ptr);
_allocator.Free(segment);
_allocator.FreeAligned(segment->Ptr, _segmentAlignment);
_allocator.FreeAligned(segment, 8);
}
// Free free pages
// Free free segments
foreach (var ip in _freeSegments)
{
Segment* segment = (Segment*)ip;
_allocator.Free(segment->Ptr);
_allocator.Free(segment);
_allocator.FreeAligned(segment->Ptr, _segmentAlignment);
_allocator.FreeAligned(segment, 8);
}
_activeSegments.Clear();
_freeSegments.Clear();
_current = null;
_totalAllocated = 0;
_totalReserved = 0;
_totalUsed = 0;
_disposed = true;
}
@@ -435,11 +795,153 @@
/// Throws an <see cref="ObjectDisposedException"/> if the <see cref="SegmentedPool"/> has already been disposed.
/// </summary>
/// <exception cref="ObjectDisposedException">
/// Thrown when this instance is no longer valid for use.
/// Thrown when this <see cref="SegmentedPool"/> instance is no longer valid for use.
/// </exception>
private void ThrowIfDisposed()
{
ObjectDisposedException.ThrowIf(_disposed, this);
}
/// <summary>
/// Gets a snapshot of the current pool state for diagnostics.
/// Thread-safe and produces no garbage.
/// </summary>
/// <returns>A <see cref="PoolState"/> containing current pool metrics.</returns>
public PoolState GetPoolState()
{
ThrowIfDisposed();
lock (_lock)
{
nuint alignment = _segmentAlignment;
nuint basePtr = (nuint)_current->Ptr;
int active = _activeSegments.Count;
int free = _freeSegments.Count;
int total = active + free;
// 1. Calculate Padding (Alignment Overhead) for Current Segment
// This is dynamic: Offset tracks total bytes written, TotalUsed tracks actual allocation bytes
nuint padding = _current->Offset - _totalUsed;
// 2. Calculate Potential Savings (Trim Projection)
nuint potentialSavings = 0;
if (free > 16)
{
int excess = free - 16;
potentialSavings = (nuint)excess * _currentSegmentSize;
}
return new PoolState
{
SegmentAlignment = alignment,
SegmentSize = _currentSegmentSize,
TotalReserved = _totalReserved,
TotalUsed = _totalUsed,
CurrentBase = basePtr,
CurrentOffset = _current->Offset,
BaseAligned = (basePtr & (alignment - 1)) == 0,
ActiveSegmentCount = active,
FreeSegmentCount = free,
TotalSegmentCount = total,
PaddingBytes = padding,
PotentialSavings = potentialSavings
};
}
}
/// <summary>
/// Generates a diagnostic report for the pool.
/// Thread-safe and produces no garbage.
/// </summary>
/// <returns>A formatted diagnostic string.</returns>
public string GetDiagnosticReport()
{
PoolState state = GetPoolState();
DiagnosticConfig config = new()
{
SegmentSize = _currentSegmentSize,
TotalReserved = _totalReserved
};
string suggestion = SegmentedPoolDiagnostics.GenerateSuggestions(state, config);
state = state with { Suggestion = suggestion };
return SegmentedPoolDiagnostics.GenerateReport(state);
}
/// <summary>
/// Helper method to construct a <see cref="SegmentInfo"/> from raw segment data.
/// </summary>
/// <param name="segment">Pointer to the segment to inspect.</param>
/// <param name="current">Pointer to the currently active segment for comparison.</param>
/// <param name="index">The logical index of the segment in the list.</param>
/// <returns>A populated <see cref="SegmentInfo"/> struct.</returns>
private SegmentInfo CreateSegmentInfo(Segment* segment, Segment* current, int index)
{
nuint alignment = _segmentAlignment;
nuint ptr = (nuint)segment->Ptr;
bool isAligned = (ptr & (alignment - 1)) == 0;
return new SegmentInfo
{
Index = index,
BaseAddress = ptr,
UsedBytes = segment->Offset,
Size = segment->Size,
IsActive = (segment == current),
AlignmentRequirement = alignment,
IsAligned = isAligned
};
}
/// <summary>
/// Gets information about the currently active segment.
/// This is the primary diagnostic view for memory usage within the active segment.
/// </summary>
/// <returns>A <see cref="SegmentInfo"/> for the current segment, or null if disposed.</returns>
public SegmentInfo GetCurrentSegmentInfo()
{
ThrowIfDisposed();
lock (_lock)
{
return CreateSegmentInfo(_current, _current, 0);
}
}
/// <summary>
/// Gets a list of all segment details for deep diagnostics.
/// Includes both active and free segments.
/// </summary>
/// <returns>A list of <see cref="SegmentInfo"/> containing all segments.</returns>
public List<SegmentInfo> GetAllSegmentInfos()
{
ThrowIfDisposed();
lock (_lock)
{
var totalSegments = _activeSegments.Count + _freeSegments.Count;
var result = new List<SegmentInfo>(totalSegments);
int currentIndex = 0;
for (int i = 0; i < _activeSegments.Count; i++)
{
IntPtr ip = _activeSegments[i];
Segment* segment = (Segment*)ip;
result.Add(CreateSegmentInfo(segment, _current, currentIndex));
currentIndex++;
}
foreach (var ip in _freeSegments)
{
Segment* segment = (Segment*)ip;
result.Add(CreateSegmentInfo(segment, _current, currentIndex++));
}
return result;
}
}
}
}

3
UnmangedMMU/UnmanagedMMU.csproj
View File

@@ -5,6 +5,9 @@
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
<GenerateDocumentationFile>true</GenerateDocumentationFile>
<!-- Optional: Suppress warnings for undocumented members -->
<NoWarn>$(NoWarn);CS1591</NoWarn>
</PropertyGroup>
</Project>

516
UnmangedMMU/WorkspaceHeap.cs Normal file
View File

@@ -0,0 +1,516 @@
namespace UnmanagedMMU
{
using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using UnmanagedMMU.Allocators;
using UnmanagedMMU.Handles;
using UnmanagedMMU.Handles.Internal;
/// <summary>
/// Provides an unmanaged heap for long-lived allocations with reuse.
/// </summary>
/// <remarks>
/// <para>
/// <see cref="WorkspaceHeap"/> minimizes calls to the underlying allocator by retaining
/// freed blocks in size-segregated free lists and reusing them when possible.
/// </para>
/// <para>
/// Allocation strategy:
/// <list type="bullet">
/// <item><description>
/// <b>Small allocations</b> (≤ 1 KB) use fixed size buckets
/// </description></item>
/// <item><description>
/// <b>Medium allocations</b> (≤ 256 KB) use best-fit reuse
/// </description></item>
/// <item><description>
/// <b>Large allocations</b> (&gt; 256 KB) use tolerance-based reuse
/// </description></item>
/// </list>
/// </para>
/// </remarks>
public unsafe sealed class WorkspaceHeap : IDisposable, IUnmanagedMemoryOwner
{
/// <summary>
/// The maximum size, in bytes, for "small" allocations. Uses fixed-size buckets
/// </summary>
private const nuint _smallThreshold = 1024;
/// <summary>
/// The maximum size, in bytes, for allocations considered "medium". Uses best-fit reuse
/// </summary>
private const nuint _mediumThreshold = 256 * 1024; // 256 KB
/// <summary>
/// The maximum absolute number of bytes that may be wasted when reusing a large block for a "large" allocation.
/// </summary>
private const nuint _largeMaxWasteBytes = 256 * 1024; // 256 KB
/// <summary>
/// The maximum allowed size ratio when reusing a large allocation block.
/// </summary>
/// <remarks>
/// For example, a value of <c>1.25</c> allows a block up to 25% larger than
/// the requested size to be reused.
/// </remarks>
private const double _largeWasteRatioLimit = 1.25;
/// <summary>
/// Predefined bucket sizes used for small allocation reuse.
/// </summary>
private static readonly nuint[] _sizeClasses =
{
32, 64, 96, 128, 160, 192, 224, 256,
288, 320, 352, 384, 416, 448, 480, 512,
544, 576, 608, 640, 672, 704, 736, 768,
800, 832, 864, 896, 928, 960, 992, 1024
};
/// <summary>
/// Allocator interface used for all underlying unmanaged memory operations.
/// </summary>
private readonly IUnmanagedAllocator _allocator;
/// <summary>
/// Internal lock, ensures thread safety while maintaining a simple interface
/// </summary>
private readonly Lock _lock = new();
/// <summary>
/// Free lists for small allocations, keyed by the bucket size, in bytes.
/// </summary>
/// <remarks>
/// For a given bucket, the corresponding stack contains previously allocated blocks that are available to be used
/// </remarks>
private readonly Dictionary<nuint, Stack<IntPtr>> _smallFree = new();
/// <summary>
/// Free lists for medium allocations keyed by the exactly allocated size, in bytes, and sorted for best-fit.
/// </summary>
private readonly SortedDictionary<nuint, Stack<IntPtr>> _mediumFree = new();
/// <summary>
/// Free lists for large allocations keyed by the exactly allocated size, in bytes, sorted for tolerance-based reuse.
/// </summary>
private readonly SortedDictionary<nuint, Stack<IntPtr>> _largeFree = new();
/// <summary>
/// Tracks the total bytes of memory reserved from the provided <see cref="IUnmanagedAllocator"/>.
/// </summary>
private nuint _totalReserved;
/// <summary>
/// Total memory currently in use by active allocations, in bytes.
/// </summary>
private nuint _totalInUse;
/// <summary>
/// Counts actual underlying OS allocations.
/// </summary>
private nuint _totalAllocations;
/// <summary>
/// Indicates whether this <see cref="WorkspaceHeap"/> has been disposed.
/// </summary>
private volatile bool _disposed;
/// <summary>
/// Internal header prepended to each allocation to track its size.
/// </summary>
[StructLayout(LayoutKind.Sequential)]
private struct BlockHeader
{
/// <summary>
/// Size of the allocation in bytes.
/// </summary>
public nuint Size;
/// <summary>
/// Padding to ensure <see cref="BlockHeader"></see> is 32-byte aligned
/// </summary>
private readonly nuint _pad1;
/// <summary>
/// Padding to ensure <see cref="BlockHeader"></see> is 32-byte aligned
/// </summary>
private readonly nuint _pad2;
/// <summary>
/// Padding to ensure <see cref="BlockHeader"></see> is 32-byte aligned
/// </summary>
private readonly nuint _pad3;
}
/// <summary>
/// Creates a new <see cref="WorkspaceHeap"/>.
/// </summary>
public WorkspaceHeap()
: this(new DefaultUnmanagedAllocator())
{
}
/// <summary>
/// Creates a new <see cref="WorkspaceHeap"/> using the specified <see cref="IUnmanagedAllocator"/>.
/// </summary>
/// <param name="allocator">Allocator implementing <see cref="IUnmanagedAllocator"/>.</param>
internal WorkspaceHeap(IUnmanagedAllocator allocator)
{
_allocator = allocator;
// Initialize small-size buckets
foreach (var size in _sizeClasses)
_smallFree[size] = new Stack<IntPtr>();
}
/// <summary>
/// Gets the total number of bytes currently allocated from the underlying allocator.
/// </summary>
/// <remarks>
/// This includes both active allocations and freed blocks retained for reuse.
/// </remarks>
public nuint TotalReservedBytes
{
get
{
lock (_lock)
return _totalReserved;
}
}
/// <summary>
/// Gets the total number of bytes currently in use by active allocations.
/// </summary>
/// <remarks>
/// This value decreases when memory is freed and increases when new allocations occur.
/// </remarks>
public nuint TotalUsedBytes
{
get
{
lock (_lock)
{
return _totalInUse;
}
}
}
/// <summary>
/// Gets the total number of allocation operations performed by this heap.
/// </summary>
/// <remarks>
/// This counts new underlying OS allocations, not reuse from free lists.
/// Useful for performance diagnostics and testing reuse behavior.
/// </remarks>
public nuint TotalAllocationCount
{
get
{
lock (_lock)
{
return _totalAllocations;
}
}
}
/// <summary>
/// Indicates whether the <see cref="WorkspaceHeap"/> has been disposed.
/// </summary>
public bool IsDisposed
{
get { return _disposed; }
}
/// <summary>
/// Determines the small size bucket for a requested allocation.
/// </summary>
/// <param name="size">The allocation size to get the bucket size for</param>
/// <returns>The small size bucket for the requested allocation</returns>
private static nuint GetSizeClass(nuint size)
{
foreach (nuint s in _sizeClasses)
{
if (size <= s)
{
return s;
}
}
return size;
}
/// <summary>
/// Allocates a new block from the underlying allocator including a header.
/// </summary>
/// <param name="payloadSize">Requested payload size in bytes.</param>
/// <returns>
/// Pointer to the allocated block (header included).
/// </returns>
private IntPtr AllocateNew(nuint payloadSize)
{
nuint total = payloadSize + (nuint)sizeof(BlockHeader);
void* raw = _allocator.Alloc(total);
_totalReserved += total;
_totalAllocations++;
return (IntPtr)raw;
}
/// <summary>
/// Allocates unmanaged memory from the workspace heap.
/// </summary>
/// <param name="count">Number of elements <typeparamref name="T"/> to allocate.</param>
/// <param name="zero">If true, memory is zero-initialized.</param>
/// <returns> An <see cref="IMemoryHandle{T}"/> to the allocated memory.</returns>
/// <exception cref="ObjectDisposedException">Thrown if heap is disposed.</exception>
/// <exception cref="ArgumentOutOfRangeException">Thrown if size is zero.</exception>
public IMemoryHandle<T> Allocate<T>(int count, bool zero = false) where T : unmanaged
{
ArgumentOutOfRangeException.ThrowIfNegative(count);
ArgumentOutOfRangeException.ThrowIfZero(count);
if ((nuint)count > nuint.MaxValue / (nuint)(sizeof(T)))
{
throw new OverflowException($"Requested allocation of {count} elements of type {typeof(T)} exceeds allowable maximum memory size.");
}
nuint size = (nuint)count * (nuint)sizeof(T);
lock (_lock)
{
ThrowIfDisposed();
void* ptr = null;
if (size <= _smallThreshold)
{
ptr = AllocateSmall(size, zero);
}
else if (size <= _mediumThreshold)
{
ptr = AllocateMedium(size, zero);
}
else
{
ptr = AllocateLarge(size, zero);
}
return new PersistentMemoryHandle<T>((T*)ptr, size, this);
}
}
/// <summary>Allocates a small-size block using bucketed free lists.</summary>
private void* AllocateSmall(nuint size, bool zero)
{
nuint bucket = GetSizeClass(size);
Stack<IntPtr> stack = _smallFree[bucket];
IntPtr block = stack.Count > 0
? stack.Pop()
: AllocateNew(bucket);
BlockHeader* header = (BlockHeader*)block;
header->Size = bucket;
_totalInUse += bucket;
void* user = header + 1;
if (zero)
Unsafe.InitBlockUnaligned(user, 0, (uint)bucket);
return user;
}
/// <summary>Allocates a medium-size block using best-fit reuse.</summary>
private void* AllocateMedium(nuint size, bool zero)
{
foreach (var kv in _mediumFree)
{
if (kv.Key >= size && kv.Value.Count > 0)
{
var block = kv.Value.Pop();
var header = (BlockHeader*)block;
_totalInUse += header->Size;
void* user = header + 1;
if (zero)
Unsafe.InitBlockUnaligned(user, 0, (uint)header->Size);
return user;
}
}
var newBlock = AllocateNew(size);
var newHeader = (BlockHeader*)newBlock;
newHeader->Size = size;
_totalInUse += size;
void* newUser = newHeader + 1;
if (zero)
{
Unsafe.InitBlockUnaligned(newUser, 0, (uint)size);
}
return newUser;
}
/// <summary>Allocates a large block using tolerance-based reuse (smallest ≥ requested within waste bounds).</summary>
private void* AllocateLarge(nuint size, bool zero)
{
foreach (var kv in _largeFree)
{
nuint blockSize = kv.Key;
if (blockSize < size || kv.Value.Count == 0)
{
continue;
}
nuint waste = blockSize - size;
bool acceptable =
waste <= _largeMaxWasteBytes ||
((double)blockSize / size) <= _largeWasteRatioLimit;
if (!acceptable)
{
continue;
}
var block = kv.Value.Pop();
var header = (BlockHeader*)block;
_totalInUse += header->Size;
void* user = header + 1;
if (zero)
{
Unsafe.InitBlockUnaligned(user, 0, (uint)header->Size);
}
return user;
}
var newBlock = AllocateNew(size);
var newHeader = (BlockHeader*)newBlock;
newHeader->Size = size;
_totalInUse += size;
void* newUser = newHeader + 1;
if (zero)
{
Unsafe.InitBlockUnaligned(newUser, 0, (uint)size);
}
return newUser;
}
/// <summary>
/// Frees a previously allocated block, returning it to the appropriate free list.
/// </summary>
void IUnmanagedMemoryOwner.Free(IOwnedHandle handle)
{
ThrowIfDisposed();
if (handle.Pointer == null)
{
return;
}
if (handle.GetOwner() != this)
{
throw new InvalidOperationException(
"Attempted to free a handle from a different allocator pool.");
}
lock (_lock)
{
var header = ((BlockHeader*)handle.Pointer) - 1;
nuint size = header->Size;
_totalInUse -= size;
if (size <= _smallThreshold)
_smallFree[size].Push((IntPtr)header);
else if (size <= _mediumThreshold)
{
if (!_mediumFree.TryGetValue(size, out var stack))
_mediumFree[size] = stack = new Stack<IntPtr>();
stack.Push((IntPtr)header);
}
else
{
if (!_largeFree.TryGetValue(size, out var stack))
_largeFree[size] = stack = new Stack<IntPtr>();
stack.Push((IntPtr)header);
}
}
}
/// <summary>
/// Releases all unused blocks back to the underlying allocator.
/// </summary>
public void Prune()
{
ThrowIfDisposed();
lock (_lock)
{
PruneDictionary(_smallFree);
PruneDictionary(_mediumFree);
PruneDictionary(_largeFree);
}
}
/// <summary>Helper to free all blocks in a dictionary of free stacks.</summary>
private void PruneDictionary(IDictionary<nuint, Stack<IntPtr>> dict)
{
foreach (var kv in dict)
{
var stack = kv.Value;
while (stack.Count > 0)
{
var block = stack.Pop();
var header = (BlockHeader*)block;
_allocator.Free((void*)block);
_totalReserved -= (header->Size + (nuint)sizeof(BlockHeader));
}
}
}
/// <summary>
/// Releases all memory and marks the heap as disposed.
/// </summary>
public void Dispose()
{
if (_disposed)
{
return;
}
lock (_lock)
{
if (_disposed)
{
return;
}
if (_totalInUse > 0)
{
throw new InvalidOperationException(
"Cannot dispose WorkspaceHeap while active allocations exist. " +
"Dispose all handles returned from this heap before disposing the heap.");
}
Prune();
// Reset stats
_totalInUse = 0;
_totalAllocations = 0;
_disposed = true;
}
}
/// <summary>
/// Throws an <see cref="ObjectDisposedException"/> if the <see cref="WorkspaceHeap"/> has already been disposed.
/// </summary>
/// <exception cref="ObjectDisposedException">
/// Thrown when this instance is no longer valid for use.
/// </exception>
private void ThrowIfDisposed()
{
ObjectDisposedException.ThrowIf(_disposed, this);
}
}
}