Re: [POLL] SLAB : Are the 32 and 192 bytes caches really usefull on x86_64 machines ?

[Dave Jones <davej@redhat.com>]

 > Something like this:
 > 
 > http://lwn.net/Articles/124374/

One thing that really sticks out like a sore thumb is soft_cursor()
That thing gets called a *lot*, and every time it does a kmalloc/free
pair that 99.9% of the time is going to be the same size alloc as
it was the last time.  This patch makes that alloc persistent
(and does a realloc if the size changes).
The only time it should change is if the font/resolution changes I think.

Boot tested with vesafb & fbconsole, which had the desired effect.
With this patch, it almost falls off the profile.

Signed-off-by: Dave Jones <davej@redhat.com>

--- linux-2.6.14/drivers/video/console/softcursor.c~	2005-12-28 18:40:08.000000000 -0500
+++ linux-2.6.14/drivers/video/console/softcursor.c	2005-12-28 18:45:50.000000000 -0500
@@ -23,7 +23,9 @@ int soft_cursor(struct fb_info *info, st
 	unsigned int buf_align = info->pixmap.buf_align - 1;
 	unsigned int i, size, dsize, s_pitch, d_pitch;
 	struct fb_image *image;
-	u8 *dst, *src;
+	u8 *dst;
+	static u8 *src=NULL;
+	static int allocsize=0;
 
 	if (info->state != FBINFO_STATE_RUNNING)
 		return 0;
@@ -31,9 +33,15 @@ int soft_cursor(struct fb_info *info, st
 	s_pitch = (cursor->image.width + 7) >> 3;
 	dsize = s_pitch * cursor->image.height;
 
-	src = kmalloc(dsize + sizeof(struct fb_image), GFP_ATOMIC);
-	if (!src)
-		return -ENOMEM;
+	if (dsize + sizeof(struct fb_image) != allocsize) {
+		if (src != NULL)
+			kfree(src);
+		allocsize = dsize + sizeof(struct fb_image);
+
+		src = kmalloc(allocsize, GFP_ATOMIC);
+		if (!src)
+			return -ENOMEM;
+	}
 
 	image = (struct fb_image *) (src + dsize);
 	*image = cursor->image;
@@ -61,7 +69,6 @@ int soft_cursor(struct fb_info *info, st
 	fb_pad_aligned_buffer(dst, d_pitch, src, s_pitch, image->height);
 	image->data = dst;
 	info->fbops->fb_imageblit(info, image);
-	kfree(src);
 	return 0;
 }