diff --git a/dlls/ntdll/heap.c b/dlls/ntdll/heap.c
index a908f19..9cd5c5c 100644
--- a/dlls/ntdll/heap.c
+++ b/dlls/ntdll/heap.c
@@ -114,9 +114,27 @@
     ((flags & HEAP_TAIL_CHECKING_ENABLED) || RUNNING_ON_VALGRIND ? ALIGNMENT : 0)
 
 /* Max size of the blocks on the free lists */
+/* NOTE. clang-cl allocates 200~500 bytes memory a lot. So, using fine
+   grained freelist improves clang-cl performance a lot (e.g. 60s -> 40s
+   to compile Node.cpp in blink on Z620.
+
+   heap freelist consists of 3 types of classes.
+   1. small (<= 512B). 16B each. 16B, 32B, 48B, ..., 512B.
+   2. large (<= 4096B). 256B each. 512B, 768B, ..., 4096B.
+   3. huge  (> 4K).
+ */
 static const SIZE_T HEAP_freeListSizes[] =
 {
-    0x10, 0x20, 0x30, 0x40, 0x60, 0x80, 0x100, 0x200, 0x400, 0x1000, ~0UL
+    /* small classes; 32 classes */
+    0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70, 0x80,
+    0x90, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0, 0x100,
+    0x110, 0x120, 0x130, 0x140, 0x150, 0x160, 0x170, 0x180,
+    0x190, 0x1A0, 0x1B0, 0x1C0, 0x1D0, 0x1E0, 0x1F0, 0x200,
+    /* large classes; 14 classes */
+    0x300, 0x400, 0x500, 0x600, 0x700, 0x800, 0x900,
+    0xA00, 0xB00, 0xC00, 0xD00, 0xE00, 0xF00, 0x1000,
+    /* huge class; 1 class */
+    ~0UL
 };
 #define HEAP_NB_FREE_LISTS  (sizeof(HEAP_freeListSizes)/sizeof(HEAP_freeListSizes[0]))
 
@@ -300,11 +318,21 @@
 /* size is the size of the whole block including the arena header */
 static inline unsigned int get_freelist_index( SIZE_T size )
 {
-    unsigned int i;
-
-    size -= sizeof(ARENA_FREE);
-    for (i = 0; i < HEAP_NB_FREE_LISTS - 1; i++) if (size <= HEAP_freeListSizes[i]) break;
-    return i;
+    /* Note: this index is based on HEAP_freeListSizes. */
+    if (size == 0) {
+        return 0;
+    }
+    /* For small class, 16B each. */
+    if (size <= 0x200) {
+        return (size - 1) / 0x10;
+    }
+    /* For large class, 256B each */
+    if (size <= 0x1000) {
+        return (size - 1) / 0x100 + 30;
+    }
+    /* For huge class. Only 1 index. */
+    /* HEAP_NB_FREE_LISTS should be 47 now. */
+    return HEAP_NB_FREE_LISTS - 1;
 }
 
 /* get the memory protection type to use for a given heap */
@@ -466,7 +494,7 @@
  */
 static inline void HEAP_InsertFreeBlock( HEAP *heap, ARENA_FREE *pArena, BOOL last )
 {
-    FREE_LIST_ENTRY *pEntry = heap->freeList + get_freelist_index( pArena->size + sizeof(*pArena) );
+    FREE_LIST_ENTRY *pEntry = heap->freeList + get_freelist_index( pArena->size );
     if (last)
     {
         /* insert at end of free list, i.e. before the next free list entry */
@@ -992,7 +1020,7 @@
     SUBHEAP *subheap;
     struct list *ptr;
     SIZE_T total_size;
-    FREE_LIST_ENTRY *pEntry = heap->freeList + get_freelist_index( size + sizeof(ARENA_INUSE) );
+    FREE_LIST_ENTRY *pEntry = heap->freeList + get_freelist_index( size );
 
     /* Find a suitable free list, and in it find a block large enough */
 
@@ -1001,7 +1029,8 @@
     {
         ARENA_FREE *pArena = LIST_ENTRY( ptr, ARENA_FREE, entry );
         SIZE_T arena_size = (pArena->size & ARENA_SIZE_MASK) +
-                            sizeof(ARENA_FREE) - sizeof(ARENA_INUSE);
+                             sizeof(ARENA_FREE) - sizeof(ARENA_INUSE);
+
         if (arena_size >= size)
         {
             subheap = HEAP_FindSubHeap( heap, pArena );