Hi Thomas,
On Thu, Feb 17, 2022 at 11:34:04AM +0100, Thomas Zimmermann wrote:
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@suse.de
Nice optimization. Reviewed-by: Sam Ravnborg sam@ravnborg.org
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