diff mbox series

aarch64: revert memcpy optimze for kunpeng to avoid performance degradation

Message ID 20210120072044.23228-1-wangshuo47@huawei.com
State Committed
Commit 28f2ce27722d890a884cc7fa2f6d2bc0cb418f26
Headers show
Series aarch64: revert memcpy optimze for kunpeng to avoid performance degradation | expand

Commit Message

Shuo Wang Jan. 20, 2021, 7:20 a.m. UTC
In commit 863d775c481704baaa41855fc93e5a1ca2dc6bf6, kunpeng920 is added to default memcpy version,
however, there is performance degradation when the copy size is some large bytes, eg: 100k. 
This is the result, tested in glibc-2.28:
             before backport  after backport	 Performance improvement
memcpy_1k      0.005              0.005                 0.00%
memcpy_10k     0.032              0.029                 10.34%
memcpy_100k    0.356              0.429                 -17.02%
memcpy_1m      7.470              11.153                -33.02%

This is the demo
#include "stdio.h"
#include "string.h"
#include "stdlib.h"

char a[1024*1024] = {12};
char b[1024*1024] = {13};
int main(int argc, char *argv[])
{
    int i = atoi(argv[1]);
    int j;
    int size = atoi(argv[2]);
    
    for (j = 0; j < i; j++)
        memcpy(b, a, size*1024);
    return 0;
}

# gcc -g -O0 memcpy.c -o memcpy
# time taskset -c 10 ./memcpy 100000 1024

Co-authored-by: liqingqing <liqingqing3@huawei.com>

---
 sysdeps/aarch64/multiarch/memcpy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Adhemerval Zanella Jan. 20, 2021, 1:09 p.m. UTC | #1
Hi,

Since I don't have access to this specific hardware, it would be good
if the original author, Xuelei Zhang, of the change could certify this
reversion is ok.

It should be ok during the freeze since it just a selection of an
already tested implementation for an specific chip implementation.

On 20/01/2021 04:20, Shuo Wang wrote:
> In commit 863d775c481704baaa41855fc93e5a1ca2dc6bf6, kunpeng920 is added to default memcpy version,
> however, there is performance degradation when the copy size is some large bytes, eg: 100k. 
> This is the result, tested in glibc-2.28:
>              before backport  after backport	 Performance improvement
> memcpy_1k      0.005              0.005                 0.00%
> memcpy_10k     0.032              0.029                 10.34%
> memcpy_100k    0.356              0.429                 -17.02%
> memcpy_1m      7.470              11.153                -33.02%
> 
> This is the demo
> #include "stdio.h"
> #include "string.h"
> #include "stdlib.h"
> 
> char a[1024*1024] = {12};
> char b[1024*1024] = {13};
> int main(int argc, char *argv[])
> {
>     int i = atoi(argv[1]);
>     int j;
>     int size = atoi(argv[2]);
>     
>     for (j = 0; j < i; j++)
>         memcpy(b, a, size*1024);
>     return 0;
> }
> 
> # gcc -g -O0 memcpy.c -o memcpy
> # time taskset -c 10 ./memcpy 100000 1024
> 
> Co-authored-by: liqingqing <liqingqing3@huawei.com>
> 
> ---
>  sysdeps/aarch64/multiarch/memcpy.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sysdeps/aarch64/multiarch/memcpy.c b/sysdeps/aarch64/multiarch/memcpy.c
> index 27259d3386..0e0a5cbcfb 100644
> --- a/sysdeps/aarch64/multiarch/memcpy.c
> +++ b/sysdeps/aarch64/multiarch/memcpy.c
> @@ -37,7 +37,7 @@ extern __typeof (__redirect_memcpy) __memcpy_falkor attribute_hidden;
>  libc_ifunc (__libc_memcpy,
>              (IS_THUNDERX (midr)
>  	     ? __memcpy_thunderx
> -	     : (IS_FALKOR (midr) || IS_PHECDA (midr) || IS_KUNPENG920 (midr)
> +	     : (IS_FALKOR (midr) || IS_PHECDA (midr)
>  		? __memcpy_falkor
>  		: (IS_THUNDERX2 (midr) || IS_THUNDERX2PA (midr)
>  		  ? __memcpy_thunderx2
>
diff mbox series

Patch

diff --git a/sysdeps/aarch64/multiarch/memcpy.c b/sysdeps/aarch64/multiarch/memcpy.c
index 27259d3386..0e0a5cbcfb 100644
--- a/sysdeps/aarch64/multiarch/memcpy.c
+++ b/sysdeps/aarch64/multiarch/memcpy.c
@@ -37,7 +37,7 @@  extern __typeof (__redirect_memcpy) __memcpy_falkor attribute_hidden;
 libc_ifunc (__libc_memcpy,
             (IS_THUNDERX (midr)
 	     ? __memcpy_thunderx
-	     : (IS_FALKOR (midr) || IS_PHECDA (midr) || IS_KUNPENG920 (midr)
+	     : (IS_FALKOR (midr) || IS_PHECDA (midr)
 		? __memcpy_falkor
 		: (IS_THUNDERX2 (midr) || IS_THUNDERX2PA (midr)
 		  ? __memcpy_thunderx2