mirror of https://gitee.com/openkylin/linux.git
efdb25efc7
Improve the performance of the crc32() asm routines by getting rid of
most of the branches and small sized loads on the common path.
Instead, use a branchless code path involving overlapping 16 byte
loads to process the first (length % 32) bytes, and process the
remainder using a loop that processes 32 bytes at a time.
Tested using the following test program:
#include <stdlib.h>
extern void crc32_le(unsigned short, char const*, int);
int main(void)
{
static const char buf[4096];
srand(20181126);
for (int i = 0; i < 100 * 1000 * 1000; i++)
crc32_le(0, buf, rand() % 1024);
return 0;
}
On Cortex-A53 and Cortex-A57, the performance regresses but only very
slightly. On Cortex-A72 however, the performance improves from
$ time ./crc32
real 0m10.149s
user 0m10.149s
sys 0m0.000s
to
$ time ./crc32
real 0m7.915s
user 0m7.915s
sys 0m0.000s
Cc: Rui Sun <sunrui26@huawei.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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|---|---|---|
| .. | ||
| Makefile | ||
| atomic_ll_sc.c | ||
| clear_page.S | ||
| clear_user.S | ||
| copy_from_user.S | ||
| copy_in_user.S | ||
| copy_page.S | ||
| copy_template.S | ||
| copy_to_user.S | ||
| crc32.S | ||
| delay.c | ||
| memchr.S | ||
| memcmp.S | ||
| memcpy.S | ||
| memmove.S | ||
| memset.S | ||
| strchr.S | ||
| strcmp.S | ||
| strlen.S | ||
| strncmp.S | ||
| strnlen.S | ||
| strrchr.S | ||
| tishift.S | ||
| uaccess_flushcache.c | ||