hlsf wrong slicing solving

StgSharp.Common/HighPerformance/Memory/HLSFAllocator.SegmentEntry.cs

@@ -108,7 +108,15 @@ namespace StgSharp.HighPerformance.Memory
         /// </summary>
         private void MergeAndRemoveFromBuckets(Entry* entry)
         {
-            if (entry == null) {
+            // 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;
             }
 
@@ -130,14 +138,16 @@ namespace StgSharp.HighPerformance.Memory
                     // 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) ||
-                        entry->Level != prev->Level ||
-                        !TryRemoveFromBucket(originLevel, DetermineSegmentIndex(prev->Size, originLevel), (BucketNode*)prev->Position))
+                    if (prev != null &&
+                        prev != _spareMemory &&
+                        AssertBackwardBoundary(currentOffset, prev, originLevel) &&
+                        IsAdjacentTo(entry, prev) &&
+                        TryRemoveFromBucket(originLevel, DetermineSegmentIndex(prev->Size, originLevel), (BucketNode*)prev->Position))
                     {
-                        break;
+                        // Merge
+                        entry->Position = prev->Position;
+                        entry->Size += prev->Size;
+                        RemoveFromPositionChain(prev);
                     }
 
                     // Update linked list
@@ -148,11 +158,6 @@ namespace StgSharp.HighPerformance.Memory
                     }
                     entry->PreviousNear = prevPrev;
                     /**/
-
-                    // Merge
-                    entry->Position = prev->Position;
-                    entry->Size += prev->Size;
-                    RemoveFromPositionChain(prev);
                 }
 
                 while (true)
@@ -189,19 +194,6 @@ namespace StgSharp.HighPerformance.Memory
             } while (originLevel < entry->Level);
         }
 
-        private void RecycleEntry(Entry* entry)
-        {
-            if (entry is null) {
-                return;
-            }
-
-            entry->PreviousNear = null;
-            entry->NextNear = null;
-
-            // Console.WriteLine("entry recycled.");
-            _entries.Free((nuint)entry);
-        }
-
         /// <summary>
         ///   Remove node from position linked list
         /// </summary>
@@ -246,6 +238,7 @@ namespace StgSharp.HighPerformance.Memory
         internal enum EntryState : uint
         {
 
+            Spare,
             Empty,
             Allocated