heap

source/Cosmos.Core.Memory.Test/Heap.cs

@@ -8,12 +8,12 @@ using Native = System.UInt32;
 namespace Cosmos.Core.Memory.Test {
 
   unsafe static public class Heap {
-  
+
     static public byte* Alloc(Native aSize) {
-      //TODO - Dont use medium if its close to the page size - does'nt make sense to make a medium page
-      // with only enough free space for something that would be small anyway.
-      if (aSize <= RAT.PageSize - HeapMedium.PrefixBytes) {
-        return HeapLarge.Alloc(aSize);
+      if (aSize <= HeapSmall.MaxItemSize) {
+        return HeapSmall.Alloc(aSize);
+      } else if (aSize <= HeapMedium.MaxItemSize) {
+        return HeapMedium.Alloc(aSize);
       } else {
         return HeapLarge.Alloc(aSize);
       }

source/Cosmos.Core.Memory.Test/HeapMedium.cs

@@ -8,5 +8,18 @@ using Native = System.UInt32;
 namespace Cosmos.Core.Memory.Test {
   unsafe static public class HeapMedium {
     public const Native PrefixBytes = 4 * sizeof(Native);
+    // TODO Adjust when page size changes from 4k to 2/4mb
+    // Also adjust according to heap stats and final adjustments to small heap. ie the -1024 should be at least size of 
+    // max small heap else it will never get used;
+    // HeapMedium may be of limited use with 4k pages depending on the final sizes of the small heap.
+    public const Native MaxItemSize = RAT.PageSize - 1024;
+
+    static public byte* Alloc(Native aSize) {
+      return HeapLarge.Alloc(aSize);
+    }
+
+    static public void Free(void* aPtr) {
+      HeapLarge.Free(aPtr);
+    }
   }
 }

source/Cosmos.Core.Memory.Test/HeapSmall.cs

@@ -3,8 +3,19 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
+using Native = System.UInt32;
 
 namespace Cosmos.Core.Memory.Test {
   unsafe static public class HeapSmall {
+    public const Native PrefixBytes = 4 * sizeof(Native);
+    public const Native MaxItemSize = 1024 - PrefixBytes;
+
+    static public byte* Alloc(Native aSize) {
+      return HeapLarge.Alloc(aSize);
+    }
+
+    static public void Free(void* aPtr) {
+      HeapLarge.Free(aPtr);
+    }
   }
 }

source/Cosmos.Core.Memory.Test/RAT.cs

@@ -29,7 +29,7 @@ namespace Cosmos.Core.Memory.Test {
     // Native Intel page size
     // x86 Page Size: 4k, 2m (PAE only), 4m
     // x64 Page Size: 4k, 2m
-    static public readonly Native PageSize = 4096;
+    public const Native PageSize = 4096;
 
     // Start of area usable for heap, and also start of heap.
     static private byte* mRamStart;

source/Cosmos.Core.Memory.Test/UnitTest1.cs

@@ -7,7 +7,7 @@ namespace Cosmos.Core.Memory.Test {
   public class UnitTest1 {
     [TestMethod]
     unsafe public void TestMethod1() {
-      var xRAM = new byte[128 * 1024 * 1024];
+      var xRAM = new byte[128 * 1024 * 1024]; // 128 MB
       xRAM[0] = 1;
       fixed (byte* xPtr = xRAM) {
         RAT.Debug = true;