Re: [PATCH 1/1 2.6.13] framebuffer: bit_putcs() optimization for 8x* fonts

[Knut Petersen <Knut_Petersen@t-online.de>]

>Something like below, which has the advantange that there is still only 
>one implementation of the function
>
True, that´s a great advantage.

> and if it's still slower, we really need to check the compiler
>  
>
Please have a look at the following patch. It takes your idea of 
inlining but moves
the special cases into the macro, speeding things up for the very likely 
case of
s_pitch == 1 and the less likely case of s_pitch of 2. Treating s_pitch 
== 2 special
gives a still significant performance improvement of more than 10 % for 
16x30
fonts.

This way also bit_putcs looks better again ...

Andrew, as this way is better than and still as fast as my first 
approach I think
framebuffer-bit_putcs-optimization-for-8x.patch should be reverted and the
following patch should be applied instead.

Antonino, Roman, Geert, do you agree?


cu,
 knut

diff -uprN -X linux/Documentation/dontdiff -x '*.bak' -x '*.ctx' linuxorig/drivers/video/console/bitblit.c linux/drivers/video/console/bitblit.c
--- linuxorig/drivers/video/console/bitblit.c	2005-08-29 01:41:01.000000000 +0200
+++ linux/drivers/video/console/bitblit.c	2005-08-31 10:06:22.000000000 +0200
@@ -175,7 +175,7 @@ static void bit_putcs(struct vc_data *vc
 					src = buf;
 				}
 
-				fb_pad_aligned_buffer(dst, pitch, src, idx, image.height);
+				__fb_pad_aligned_buffer(dst, pitch, src, idx, image.height);
 				dst += width;
 			}
 		}
diff -uprN -X linux/Documentation/dontdiff -x '*.bak' -x '*.ctx' linuxorig/drivers/video/fbmem.c linux/drivers/video/fbmem.c
--- linuxorig/drivers/video/fbmem.c	2005-08-29 01:41:01.000000000 +0200
+++ linux/drivers/video/fbmem.c	2005-08-31 13:36:16.000000000 +0200
@@ -80,15 +80,7 @@ EXPORT_SYMBOL(fb_get_color_depth);
  */
 void fb_pad_aligned_buffer(u8 *dst, u32 d_pitch, u8 *src, u32 s_pitch, u32 height)
 {
-	int i, j;
-
-	for (i = height; i--; ) {
-		/* s_pitch is a few bytes at the most, memcpy is suboptimal */
-		for (j = 0; j < s_pitch; j++)
-			dst[j] = src[j];
-		src += s_pitch;
-		dst += d_pitch;
-	}
+	__fb_pad_aligned_buffer(dst, d_pitch, src, s_pitch, height);
 }
 EXPORT_SYMBOL(fb_pad_aligned_buffer);
 
diff -uprN -X linux/Documentation/dontdiff -x '*.bak' -x '*.ctx' linuxorig/include/linux/fb.h linux/include/linux/fb.h
--- linuxorig/include/linux/fb.h	2005-08-29 01:41:01.000000000 +0200
+++ linux/include/linux/fb.h	2005-08-31 12:45:08.000000000 +0200
@@ -824,6 +824,38 @@ extern int fb_get_color_depth(struct fb_
 extern int fb_get_options(char *name, char **option);
 extern int fb_new_modelist(struct fb_info *info);
 
+
+/*
+ * Don't change without testing performance of framebuffer
+ * bitblitting. Inlining is necessary for performance reasons.
+ * Although the code might not _look_ fast because of some
+ * multiplications, it really _is_ fast as it is easier for gcc
+ * to optimize well.
+ */
+
+static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch, u8 *src, 
+						u32 s_pitch, u32 height)
+{
+	int i, j;
+
+	if (likely(s_pitch==1))
+		for(i=0; i < height; i++)
+			dst[d_pitch*i] = src[i];
+	else if (s_pitch==2)
+		for(i=0; i < height; i++) {
+			*(u16 *)dst = ((u16 *)src)[i];
+			dst += d_pitch;
+		}
+	else {
+		d_pitch -= s_pitch;
+		for (i = height; i--; ) {
+			for (j = 0; j < s_pitch; j++)
+				*dst++ = *src++;
+			dst += d_pitch;
+		}
+	}
+}
+
 extern struct fb_info *registered_fb[FB_MAX];
 extern int num_registered_fb;
 






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