Hi Thomas,
On 23.02.2022 20:38, Thomas Zimmermann wrote:
Improve the performance of cfb_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 cfb_imageblit() after a stabilizing period of a few minutes (i7-4790, FullHD, simpledrm, kernel with debugging).
cfb_imageblit(), new: 15724 cycles cfb_imageblit(): old: 30566 cycles
In the optimized case, cfb_imageblit() is now ~2x faster than before.
v3:
- fix commit description (Pekka)
Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Acked-by: Sam Ravnborg sam@ravnborg.org Reviewed-by: Javier Martinez Canillas javierm@redhat.com
This patch landed recently in linux next-20220308 as commit 0d03011894d2 ("fbdev: Improve performance of cfb_imageblit()"). Sadly it causes a freeze after DRM and emulated fbdev initialization on various Samsung Exynos ARM 32bit based boards. This happens when kernel is compiled from exynos_defconfig. Surprisingly when kernel is compiled from multi_v7_defconfig all those boards boot fine, so this is a matter of one of the debugging options enabled in the exynos_defconfig. I will try to analyze this further and share the results. Reverting $subject on top of next-20220308 fixes the boot issue.
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; }
Best regards