Improve the performance of sys_fillrect() by using word-aligned
32/64-bit mov instructions. While the code tried to implement this,
the compiler failed to create fast instructions. The resulting
binary instructions were even slower than cfb_fillrect(), which
uses the same algorithm, but operates on I/O memory.
A microbenchmark measures the average number of CPU cycles
for sys_fillrect() after a stabilizing period of a few minutes
(i7-4790, FullHD, simpledrm, kernel with debugging). The value
for CFB is given as a reference.
sys_fillrect(), new: 26586 cycles
sys_fillrect(), old: 166603 cycles
cfb_fillrect(): 41012 cycles
In the optimized case, sys_fillrect() is now ~6x faster than before
and ~1.5x faster than the CFB implementation.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
drivers/video/fbdev/core/sysfillrect.c | 16 +++-------------
1 file changed, 3 insertions(+), 13 deletions(-)
diff --git a/drivers/video/fbdev/core/sysfillrect.c b/drivers/video/fbdev/core/sysfillrect.c
index 33ee3d34f9d2..bcdcaeae6538 100644
--- a/drivers/video/fbdev/core/sysfillrect.c
+++ b/drivers/video/fbdev/core/sysfillrect.c
@@ -50,19 +50,9 @@ bitfill_aligned(struct fb_info *p, unsigned long *dst, int dst_idx,
/* Main chunk */
n /= bits;
- while (n >= 8) {
- *dst++ = pat;
- *dst++ = pat;
- *dst++ = pat;
- *dst++ = pat;
- *dst++ = pat;
- *dst++ = pat;
- *dst++ = pat;
- *dst++ = pat;
- n -= 8;
- }
- while (n--)
- *dst++ = pat;
+ memset_l(dst, pat, n);
+ dst += n;
+
/* Trailing bits */
if (last)
*dst = comp(pat, *dst, last);
--
2.34.1
