Realloc called too often in FcCharSetPutLeaf

[Michal Novotny <michal@xxxxxxxxxxxx>]

Hi,

I was looking at performance of FireFox3 startup using callgrind and 
found a lot of calls to realloc() from FcCharSetPutLeaf(). During the 
startup there are 10 calls to FcFontSort() that lead to 105242 calls to 
FcCharSetPutLeaf() and 209842 calls to realloc(). I tried to 
allocate/reallocate memory in bigger blocks and calls to realloc() were 
reduced to 25982 when block size was 8 (patch is attached). Of course 
some memory is wasted with this approach but number of instructions 
needed to do FcFontSort() decreased from 176569552 to 125762052. Is it 
possible to have similar optimalization in next releases of fontconfig?

Michal


diff --git a/src/fccharset.c b/src/fccharset.c
index 5da1312..027cab1 100644
--- a/src/fccharset.c
+++ b/src/fccharset.c
@@ -130,46 +130,54 @@ FcCharSetPutLeaf (FcCharSet	*fcs,
 {
     intptr_t	*leaves = FcCharSetLeaves (fcs);
     FcChar16	*numbers = FcCharSetNumbers (fcs);
+    int capacity;
 
     ucs4 >>= 8;
     if (ucs4 >= 0x10000)
 	return FcFalse;
-    if (!fcs->num)
-	leaves = malloc (sizeof (*leaves));
-    else
+
+    capacity = (((fcs->num) >> 3) << 3);
+    if ((fcs->num) % 8)
+      capacity += 8;
+
+    if (( fcs->num + 1) > capacity )
     {
-	intptr_t    *new_leaves = realloc (leaves, (fcs->num + 1) * 
-					   sizeof (*leaves));
-	intptr_t    distance = (intptr_t) new_leaves - (intptr_t) leaves;
-	
-	if (new_leaves && distance)
+        if (! fcs->num)
+    	    leaves = malloc ((capacity + 8) * sizeof (*leaves));
+	else
 	{
-	    int i;
+	    intptr_t    *new_leaves = realloc (leaves, (capacity + 8) * 
+						sizeof (*leaves));
+	    intptr_t    distance = (intptr_t) new_leaves - (intptr_t) leaves;
+	
+	    if (new_leaves && distance)
+	    {
+		int i;
 
-	    for (i = 0; i < fcs->num; i++)
-		new_leaves[i] -= distance;
+		for (i = 0; i < fcs->num; i++)
+		    new_leaves[i] -= distance;
+	    }
+	    leaves = new_leaves;
 	}
-	leaves = new_leaves;
-    }
-    if (!leaves)
-	return FcFalse;
-    
-    if (fcs->num)
-	FcMemFree (FC_MEM_CHARSET, fcs->num * sizeof (intptr_t));
-    FcMemAlloc (FC_MEM_CHARSET, (fcs->num + 1) * sizeof (intptr_t));
-    fcs->leaves_offset = FcPtrToOffset (fcs, leaves);
+	if (!leaves)
+	    return FcFalse;
     
-    if (!fcs->num)
-	numbers = malloc (sizeof (FcChar16));
-    else
-	numbers = realloc (numbers, (fcs->num + 1) * sizeof (FcChar16));
-    if (!numbers)
-	return FcFalse;
+	if (fcs->num)
+	    FcMemFree (FC_MEM_CHARSET, fcs->num * sizeof (intptr_t));
+	FcMemAlloc (FC_MEM_CHARSET, (fcs->num + 1) * sizeof (intptr_t));
+	fcs->leaves_offset = FcPtrToOffset (fcs, leaves);
     
-    if (fcs->num)
-	FcMemFree (FC_MEM_CHARSET, fcs->num * sizeof (FcChar16));
-    FcMemAlloc (FC_MEM_CHARSET, (fcs->num + 1) * sizeof (FcChar16));
-    fcs->numbers_offset = FcPtrToOffset (fcs, numbers);
+	if (!fcs->num)
+	    numbers = malloc ((capacity + 8) * sizeof (FcChar16));
+	else
+	    numbers = realloc (numbers, (capacity + 8) * sizeof (FcChar16));
+	if (!numbers)
+	    return FcFalse;
+	if (fcs->num)
+	    FcMemFree (FC_MEM_CHARSET, fcs->num * sizeof (FcChar16));
+	FcMemAlloc (FC_MEM_CHARSET, (fcs->num + 1) * sizeof (FcChar16));
+	fcs->numbers_offset = FcPtrToOffset (fcs, numbers);
+    }
     
     memmove (leaves + pos + 1, leaves + pos, 
 	     (fcs->num - pos) * sizeof (*leaves));

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