//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="HLSFAllocator.SegmentEntry"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
namespace StgSharp.HighPerformance.Memory
{
public unsafe partial class HybridLayerSegregatedFitAllocator
{
///
/// check out if a bucket is within the same higher-level boundary as currentOffset
///
///
///
///
///
///
///
///
///
///
///
///
///
private bool AssertBackwardBoundary(ulong currentOffset, Entry* target, int level)
{
level = int.Min(level, MaxLevel);
int nextLevelSize = levelSizeArray[level] * 4;
ulong targetHead = target->Position - (ulong)m_Buffer;
return (currentOffset / (ulong)nextLevelSize) == (targetHead / (ulong)nextLevelSize);
}
///
/// check out if a bucket is within the same higher-level boundary as currentOffset
///
///
///
///
///
///
///
///
///
///
///
///
///
private bool AssertForwardBoundary(ulong currentOffset, Entry* target, int level)
{
level = int.Min(level, MaxLevel);
int nextLevelSize = levelSizeArray[level] * 4;
ulong targetTail = target->Position - (ulong)m_Buffer + target->Size - 1;
return (currentOffset / (ulong)nextLevelSize) == (targetTail / (ulong)nextLevelSize);
}
///
/// Determine segment index based on size and originLevel
///
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private int DetermineSegmentIndex(uint size, int level)
{
level = int.Min(level, MaxLevel);
return (int)(size - 1) / levelSizeArray[level];
}
///
/// Check if two Entries are adjacent in memory
///
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static bool IsAdjacentTo(Entry* current, Entry* other)
{
// Check if this immediately follows other
return other->Position + other->Size == current->Position ||
current->Position + current->Size == other->Position;
}
///
/// Used in Free operations, efficiently remove from buckets and merge adjacent blocks.
/// Current Entry will serve as the final merged block. The Merge will be in lazy
/// strategy.
///
private void MergeAndRemoveFromBuckets(Entry* entry)
{
// TODO
/*
* 1.有限回收，最多向上收集2层（算上当前总共3层）
* 2.单层内就可以通过前后链表遍历解决，很容易做到
* 3.由于SLAB分配器内部包含快速复用路径，因而可以考虑直接进行Free掉被合并的Entry。复用成本很低（因为SLAB既没有Version也没有IEnumerable，所以不会有额外的操作计数损耗）
* 4.后续提供HLSF.Collect全量整理API，从头遍历邻接块进行彻底的合并
*/
if (entry == null)
{
return;
}
Entry* result = entry;
uint size = entry->Size;
int originLevel = entry->Level;
int segment = DetermineSegmentIndex(size, originLevel);
// RemoveFromBucket(originLevel, segment, (BucketNode*)entry->Position);
do
{
originLevel = entry->Level;
while (true)
{
// backward merging - simplified to single attempt
Entry* prev = entry->PreviousNear;
// compute offset of current block and base position
ulong currentOffset = entry->Position - (ulong)m_Buffer;
if (prev != null &&
prev != _spareMemory &&
AssertBackwardBoundary(currentOffset, prev, originLevel) &&
IsAdjacentTo(entry, prev) &&
TryRemoveFromBucket(originLevel, DetermineSegmentIndex(prev->Size, originLevel), (BucketNode*)prev->Position))
{
// Merge
entry->Position = prev->Position;
entry->Size += prev->Size;
RemoveFromPositionChain(prev);
}
// Update linked list
/*
Entry* prevPrev = prev->PreviousNear;
if (prevPrev != null) {
prevPrev->NextNear = entry;
}
entry->PreviousNear = prevPrev;
/**/
}
while (true)
{
// forward merging - simplified to single attempt
Entry* next = entry->NextNear;
ulong currentOffset = entry->Position - (ulong)m_Buffer;
if (next == null ||
next == _spareMemory ||
!AssertForwardBoundary(currentOffset, next, entry->Level) ||
!IsAdjacentTo(entry, next) ||
entry->Level != next->Level ||
!TryRemoveFromBucket(originLevel, DetermineSegmentIndex(next->Size, originLevel), (BucketNode*)next->Position))
{
break;
}
// Update linked list
/*
Entry* nextNext = next->NextNear;
if (nextNext != null) {
nextNext->PreviousNear = entry;
}
entry->NextNear = nextNext;
/**/
// Merge
entry->Size += next->Size;
RemoveFromPositionChain(next);
}
entry->Level = GetLevelFromSize(entry->Size);
} while (originLevel < entry->Level);
}
///
/// Remove node from position linked list
///
private void RemoveFromPositionChain(Entry* entry)
{
Entry* prev = entry->PreviousNear;
Entry* next = entry->NextNear;
if (prev != null) {
prev->NextNear = entry->NextNear;
}
if (next != null) {
next->PreviousNear = entry->PreviousNear;
}
// Clear node pointers
entry->NextNear = null;
entry->PreviousNear = null;
// Console.WriteLine("entry recycled.");
_entries.Free((nuint)entry);
}
///
/// Entry structure - streamlined version (only position and state information) Stored in
/// external SLAB
///
[StructLayout(LayoutKind.Explicit, Size = 36)]
internal struct Entry
{
[FieldOffset(8)] internal Entry* NextNear; // Position linked list: next pointer
[FieldOffset(16)] internal Entry* PreviousNear; // Position linked list: previous pointer
[FieldOffset(28)] internal int Level; // Level of the block in the allocator
[FieldOffset(24)] internal uint Size; // Block size information
[FieldOffset(32)] public EntryState State;
[FieldOffset(0)] public nuint Position; // Memory block position
}
internal enum EntryState : uint
{
Spare,
Empty,
Allocated
}
#region Entry Operations
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static bool IsNullOrEmptyEntryIndex(ulong index)
{
return index == 0;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static bool IsNullOrEmptyEntryIndex(Entry* entry)
{
return entry == null;
}
#endregion
}
}