From 8e0b7427482cacd9b4d5a69a13f9a43c11457323 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Thu, 5 Jan 2017 14:25:54 +0100
Subject: [PATCH] MmapPool: Merge blocks on deallocation if possible

---
 source/tanya/container/vector.d |  3 +-
 source/tanya/math/mp.d          |  4 +--
 source/tanya/memory/mmappool.d  | 53 +++++++++++++++++++--------------
 source/tanya/memory/package.d   |  4 +--
 4 files changed, 37 insertions(+), 27 deletions(-)

diff --git a/source/tanya/container/vector.d b/source/tanya/container/vector.d
index ae909cc..1316a96 100644
--- a/source/tanya/container/vector.d
+++ b/source/tanya/container/vector.d
@@ -298,6 +298,7 @@ struct Vector(T)
 	}
 
 	// Reserves memory to store len objects and initializes it.
+	// Doesn't change the length.
 	private void initialize(in size_t len)
 	{
 		reserve(len);
@@ -316,7 +317,7 @@ struct Vector(T)
                 }
                 else
                 {
-                    memset(vector + length_, 0, len * T.sizeof);
+			memset(vector + length_, 0, (len - length_) * T.sizeof);
                 }
 	}
 
diff --git a/source/tanya/math/mp.d b/source/tanya/math/mp.d
index 6ef9926..d36ec18 100644
--- a/source/tanya/math/mp.d
+++ b/source/tanya/math/mp.d
@@ -391,7 +391,7 @@ struct Integer
 				{
 					auto tmp = Integer(h);
 					tmp.subtract(rep);
-					rep = tmp.rep;
+					swap(rep, tmp.rep);
 					sign = length == 0 ? false : h.sign;
 				}
 			}
@@ -408,7 +408,7 @@ struct Integer
 				{
 					auto tmp = Integer(h);
 					tmp.subtract(rep);
-					rep = tmp.rep;
+					swap(rep, tmp.rep);
 					sign = length == 0 ? false : !sign;
 				}
 			}
diff --git a/source/tanya/memory/mmappool.d b/source/tanya/memory/mmappool.d
index 0e322af..5682b52 100644
--- a/source/tanya/memory/mmappool.d
+++ b/source/tanya/memory/mmappool.d
@@ -27,7 +27,7 @@ else version (Windows)
 }
 
 /**
- * This allocator allocates memory in regions (multiple of 4 KB for example).
+ * This allocator allocates memory in regions (multiple of 64 KB for example).
  * Each region is then splitted in blocks. So it doesn't request the memory
  * from the operating system on each call, but only if there are no large
  * enough free blocks in the available regions.
@@ -117,30 +117,17 @@ final class MmapPool : Allocator
 		{ // Split the block if needed
 			Block block2 = cast(Block) (cast(void*) block1 + blockEntrySize + size);
 			block2.prev = block1;
-			if (block1.next is null)
-			{
-				block2.next = null;
-			}
-			else
-			{
-				block2.next = block1.next.next;
-			}
-			block1.next = block2;
-
-			block1.free = false;
+			block2.next = block1.next;
 			block2.free = true;
-
 			block2.size = block1.size - blockEntrySize - size;
-			block1.size = size;
-
 			block2.region = block1.region;
-			atomicOp!"+="(block1.region.blocks, 1);
-		}
-		else
-		{
-			block1.free = false;
-			atomicOp!"+="(block1.region.blocks, 1);
+
+			block1.next = block2;
+			block1.size = size;
 		}
+		block1.free = false;
+		atomicOp!"+="(block1.region.blocks, 1);
+
 		return cast(void*) block1 + blockEntrySize;
 	}
 
@@ -185,7 +172,29 @@ final class MmapPool : Allocator
 		}
 		else
 		{
-			block.free = true;
+			// Merge blocks if neigbours are free.
+			if (block.next !is null && block.next.free)
+			{
+				block.size = blockEntrySize + block.next.size;
+				if (block.next.next !is null)
+				{
+					block.next.next.prev = block;
+				}
+				block.next = block.next.next;
+			}
+			if (block.prev !is null && block.prev.free)
+			{
+				block.size = blockEntrySize + block.size;
+				if (block.next !is null)
+				{
+					block.next.prev = block.prev;
+				}
+				block.prev.next = block.next;
+			}
+			else
+			{
+				block.free = true;
+			}
 			atomicOp!"-="(block.region.blocks, 1);
 			return true;
 		}
diff --git a/source/tanya/memory/package.d b/source/tanya/memory/package.d
index 8b27dcf..60a45a6 100644
--- a/source/tanya/memory/package.d
+++ b/source/tanya/memory/package.d
@@ -78,8 +78,8 @@ size_t alignedSize(in size_t size, in size_t alignment = 8) pure nothrow @safe @
  *
  * Params:
  * 	T         = Element type of the array being created.
- *      Init      = If should be initialized.
- *      Throws    = If $(D_PSYMBOL OutOfMemoryError) should be throwsn.
+ * 	Init      = If should be initialized.
+ * 	Throws    = If $(D_PSYMBOL OutOfMemoryError) should be throwsn.
  * 	allocator = The allocator used for getting memory.
  * 	array     = A reference to the array being changed.
  * 	length    = New array length.