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From: Thomas Zimmermann <tzimmermann@suse.de>
To: daniel@ffwll.ch, deller@gmx.de, javierm@redhat.com,
	geert@linux-m68k.org, sam@ravnborg.org, kraxel@redhat.com
Cc: linux-fbdev@vger.kernel.org,
	Thomas Zimmermann <tzimmermann@suse.de>,
	dri-devel@lists.freedesktop.org
Subject: [PATCH v2 4/5] fbdev: Improve performance of cfb_imageblit()
Date: Mon, 21 Feb 2022 20:54:09 +0100	[thread overview]
Message-ID: <20220221195410.9172-5-tzimmermann@suse.de> (raw)
In-Reply-To: <20220221195410.9172-1-tzimmermann@suse.de>

Improve the performance of sys_imageblit() by manually unrolling
the inner blitting loop and moving some invariants out. The compiler
failed to do this automatically. This change keeps cfb_imageblit()
in sync with sys_imagebit().

A microbenchmark measures the average number of CPU cycles
for sys_imageblit() after a stabilizing period of a few minutes
(i7-4790, FullHD, simpledrm, kernel with debugging).

sys_imageblit(), new: 15724 cycles
cfb_imageblit(): old: 30566 cycles

In the optimized case, cfb_imageblit() is now ~2x faster than before.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/video/fbdev/core/cfbimgblt.c | 51 +++++++++++++++++++++++-----
 1 file changed, 42 insertions(+), 9 deletions(-)

diff --git a/drivers/video/fbdev/core/cfbimgblt.c b/drivers/video/fbdev/core/cfbimgblt.c
index 01b01a279681..7361cfabdd85 100644
--- a/drivers/video/fbdev/core/cfbimgblt.c
+++ b/drivers/video/fbdev/core/cfbimgblt.c
@@ -218,23 +218,29 @@ static inline void fast_imageblit(const struct fb_image *image, struct fb_info *
 {
 	u32 fgx = fgcolor, bgx = bgcolor, bpp = p->var.bits_per_pixel;
 	u32 ppw = 32/bpp, spitch = (image->width + 7)/8;
-	u32 bit_mask, end_mask, eorx, shift;
+	u32 bit_mask, eorx;
 	const char *s = image->data, *src;
 	u32 __iomem *dst;
 	const u32 *tab = NULL;
+	size_t tablen;
+	u32 colortab[16];
 	int i, j, k;
 
 	switch (bpp) {
 	case 8:
 		tab = fb_be_math(p) ? cfb_tab8_be : cfb_tab8_le;
+		tablen = 16;
 		break;
 	case 16:
 		tab = fb_be_math(p) ? cfb_tab16_be : cfb_tab16_le;
+		tablen = 4;
 		break;
 	case 32:
-	default:
 		tab = cfb_tab32;
+		tablen = 2;
 		break;
+	default:
+		return;
 	}
 
 	for (i = ppw-1; i--; ) {
@@ -248,15 +254,42 @@ static inline void fast_imageblit(const struct fb_image *image, struct fb_info *
 	eorx = fgx ^ bgx;
 	k = image->width/ppw;
 
-	for (i = image->height; i--; ) {
-		dst = (u32 __iomem *) dst1, shift = 8; src = s;
+	for (i = 0; i < tablen; ++i)
+		colortab[i] = (tab[i] & eorx) ^ bgx;
 
-		for (j = k; j--; ) {
-			shift -= ppw;
-			end_mask = tab[(*src >> shift) & bit_mask];
-			FB_WRITEL((end_mask & eorx)^bgx, dst++);
-			if (!shift) { shift = 8; src++; }
+	for (i = image->height; i--; ) {
+		dst = (u32 __iomem *)dst1;
+		src = s;
+
+		switch (ppw) {
+		case 4: /* 8 bpp */
+			for (j = k; j; j -= 2, ++src) {
+				FB_WRITEL(colortab[(*src >> 4) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 0) & bit_mask], dst++);
+			}
+			break;
+		case 2: /* 16 bpp */
+			for (j = k; j; j -= 4, ++src) {
+				FB_WRITEL(colortab[(*src >> 6) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 4) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 2) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 0) & bit_mask], dst++);
+			}
+			break;
+		case 1: /* 32 bpp */
+			for (j = k; j; j -= 8, ++src) {
+				FB_WRITEL(colortab[(*src >> 7) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 6) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 5) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 4) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 3) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 2) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 1) & bit_mask], dst++);
+				FB_WRITEL(colortab[(*src >> 0) & bit_mask], dst++);
+			}
+			break;
 		}
+
 		dst1 += p->fix.line_length;
 		s += spitch;
 	}
-- 
2.35.1


  parent reply	other threads:[~2022-02-21 19:54 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-21 19:54 [PATCH v2 0/5] fbdev: Improve performance of fbdev console Thomas Zimmermann
2022-02-21 19:54 ` [PATCH v2 1/5] fbdev: Improve performance of sys_fillrect() Thomas Zimmermann
2022-02-21 19:54 ` [PATCH v2 2/5] fbdev: Improve performance of sys_imageblit() Thomas Zimmermann
2022-02-21 19:54 ` [PATCH v2 3/5] fbdev: Remove trailing whitespaces from cfbimgblt.c Thomas Zimmermann
2022-02-21 19:54 ` Thomas Zimmermann [this message]
2022-02-22 13:01   ` [PATCH v2 4/5] fbdev: Improve performance of cfb_imageblit() Pekka Paalanen
2022-02-22 18:48     ` Thomas Zimmermann
2022-02-21 19:54 ` [PATCH v2 5/5] drm: Add TODO item for optimizing format helpers Thomas Zimmermann

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