[v4,2/5] AArch64: Improve A64FX memset for large sizes
Commit Message
v4: Slightly tweak alignment code
Improve performance of large memsets. Simplify alignment code. For zero memset use DC ZVA,
which almost doubles performance. For non-zero memsets use the unroll8 loop which is about 10% faster.
---
Comments
The 08/09/2021 16:17, Wilco Dijkstra via Libc-alpha wrote:
> v4: Slightly tweak alignment code
>
> Improve performance of large memsets. Simplify alignment code. For zero memset use DC ZVA,
> which almost doubles performance. For non-zero memsets use the unroll8 loop which is about 10% faster.
this is OK to commit.
you should keep
Reviewed-by: Naohiro Tamura <naohirot@fujitsu.com>
in the commit message if there are only minor tweaks or no changes.
>
> ---
>
> diff --git a/sysdeps/aarch64/multiarch/memset_a64fx.S b/sysdeps/aarch64/multiarch/memset_a64fx.S
> index cf3d402ef681a9d98964d1751537945692a1ae68..6bc8ef5e0c84dbb59a57d114ae6ec8e3fa3822ad 100644
> --- a/sysdeps/aarch64/multiarch/memset_a64fx.S
> +++ b/sysdeps/aarch64/multiarch/memset_a64fx.S
> @@ -27,14 +27,11 @@
> */
>
> #define L1_SIZE (64*1024) // L1 64KB
> -#define L2_SIZE (8*1024*1024) // L2 8MB - 1MB
> +#define L2_SIZE (8*1024*1024) // L2 8MB
> #define CACHE_LINE_SIZE 256
> #define PF_DIST_L1 (CACHE_LINE_SIZE * 16) // Prefetch distance L1
> -#define ZF_DIST (CACHE_LINE_SIZE * 21) // Zerofill distance
> -#define rest x8
> +#define rest x2
> #define vector_length x9
> -#define vl_remainder x10 // vector_length remainder
> -#define cl_remainder x11 // CACHE_LINE_SIZE remainder
>
> #if HAVE_AARCH64_SVE_ASM
> # if IS_IN (libc)
> @@ -42,14 +39,6 @@
>
> .arch armv8.2-a+sve
>
> - .macro dc_zva times
> - dc zva, tmp1
> - add tmp1, tmp1, CACHE_LINE_SIZE
> - .if \times-1
> - dc_zva "(\times-1)"
> - .endif
> - .endm
> -
> .macro st1b_unroll first=0, last=7
> st1b z0.b, p0, [dst, \first, mul vl]
> .if \last-\first
> @@ -188,54 +177,30 @@ L(L1_prefetch): // if rest >= L1_SIZE
> cbnz rest, L(unroll32)
> ret
>
> -L(L2):
> - // align dst address at vector_length byte boundary
> - sub tmp1, vector_length, 1
> - ands tmp2, dst, tmp1
> - // if vl_remainder == 0
> - b.eq 1f
> - sub vl_remainder, vector_length, tmp2
> - // process remainder until the first vector_length boundary
> - whilelt p2.b, xzr, vl_remainder
> - st1b z0.b, p2, [dst]
> - add dst, dst, vl_remainder
> - sub rest, rest, vl_remainder
> - // align dstin address at CACHE_LINE_SIZE byte boundary
> -1: mov tmp1, CACHE_LINE_SIZE
> - ands tmp2, dst, CACHE_LINE_SIZE - 1
> - // if cl_remainder == 0
> - b.eq L(L2_dc_zva)
> - sub cl_remainder, tmp1, tmp2
> - // process remainder until the first CACHE_LINE_SIZE boundary
> - mov tmp1, xzr // index
> -2: whilelt p2.b, tmp1, cl_remainder
> - st1b z0.b, p2, [dst, tmp1]
> - incb tmp1
> - cmp tmp1, cl_remainder
> - b.lo 2b
> - add dst, dst, cl_remainder
> - sub rest, rest, cl_remainder
> -
> -L(L2_dc_zva):
> - // zero fill
> - mov tmp1, dst
> - dc_zva (ZF_DIST / CACHE_LINE_SIZE) - 1
> - mov zva_len, ZF_DIST
> - add tmp1, zva_len, CACHE_LINE_SIZE * 2
> - // unroll
> + // count >= L2_SIZE
> .p2align 3
> -1: st1b_unroll 0, 3
> - add tmp2, dst, zva_len
> - dc zva, tmp2
> - st1b_unroll 4, 7
> - add tmp2, tmp2, CACHE_LINE_SIZE
> - dc zva, tmp2
> - add dst, dst, CACHE_LINE_SIZE * 2
> - sub rest, rest, CACHE_LINE_SIZE * 2
> - cmp rest, tmp1 // ZF_DIST + CACHE_LINE_SIZE * 2
> - b.ge 1b
> - cbnz rest, L(unroll8)
> - ret
> +L(L2):
> + tst valw, 255
> + b.ne L(unroll8)
> + // align dst to CACHE_LINE_SIZE byte boundary
> + and tmp2, dst, CACHE_LINE_SIZE - 1
> + st1b z0.b, p0, [dst, 0, mul vl]
> + st1b z0.b, p0, [dst, 1, mul vl]
> + st1b z0.b, p0, [dst, 2, mul vl]
> + st1b z0.b, p0, [dst, 3, mul vl]
> + sub dst, dst, tmp2
> + add count, count, tmp2
> +
> + // clear cachelines using DC ZVA
> + sub count, count, CACHE_LINE_SIZE * 2
> + .p2align 4
> +1: add dst, dst, CACHE_LINE_SIZE
> + dc zva, dst
> + subs count, count, CACHE_LINE_SIZE
> + b.hi 1b
> + add count, count, CACHE_LINE_SIZE
> + add dst, dst, CACHE_LINE_SIZE
> + b L(last)
>
> END (MEMSET)
> libc_hidden_builtin_def (MEMSET)
>
--
@@ -27,14 +27,11 @@
*/
#define L1_SIZE (64*1024) // L1 64KB
-#define L2_SIZE (8*1024*1024) // L2 8MB - 1MB
+#define L2_SIZE (8*1024*1024) // L2 8MB
#define CACHE_LINE_SIZE 256
#define PF_DIST_L1 (CACHE_LINE_SIZE * 16) // Prefetch distance L1
-#define ZF_DIST (CACHE_LINE_SIZE * 21) // Zerofill distance
-#define rest x8
+#define rest x2
#define vector_length x9
-#define vl_remainder x10 // vector_length remainder
-#define cl_remainder x11 // CACHE_LINE_SIZE remainder
#if HAVE_AARCH64_SVE_ASM
# if IS_IN (libc)
@@ -42,14 +39,6 @@
.arch armv8.2-a+sve
- .macro dc_zva times
- dc zva, tmp1
- add tmp1, tmp1, CACHE_LINE_SIZE
- .if \times-1
- dc_zva "(\times-1)"
- .endif
- .endm
-
.macro st1b_unroll first=0, last=7
st1b z0.b, p0, [dst, \first, mul vl]
.if \last-\first
@@ -188,54 +177,30 @@ L(L1_prefetch): // if rest >= L1_SIZE
cbnz rest, L(unroll32)
ret
-L(L2):
- // align dst address at vector_length byte boundary
- sub tmp1, vector_length, 1
- ands tmp2, dst, tmp1
- // if vl_remainder == 0
- b.eq 1f
- sub vl_remainder, vector_length, tmp2
- // process remainder until the first vector_length boundary
- whilelt p2.b, xzr, vl_remainder
- st1b z0.b, p2, [dst]
- add dst, dst, vl_remainder
- sub rest, rest, vl_remainder
- // align dstin address at CACHE_LINE_SIZE byte boundary
-1: mov tmp1, CACHE_LINE_SIZE
- ands tmp2, dst, CACHE_LINE_SIZE - 1
- // if cl_remainder == 0
- b.eq L(L2_dc_zva)
- sub cl_remainder, tmp1, tmp2
- // process remainder until the first CACHE_LINE_SIZE boundary
- mov tmp1, xzr // index
-2: whilelt p2.b, tmp1, cl_remainder
- st1b z0.b, p2, [dst, tmp1]
- incb tmp1
- cmp tmp1, cl_remainder
- b.lo 2b
- add dst, dst, cl_remainder
- sub rest, rest, cl_remainder
-
-L(L2_dc_zva):
- // zero fill
- mov tmp1, dst
- dc_zva (ZF_DIST / CACHE_LINE_SIZE) - 1
- mov zva_len, ZF_DIST
- add tmp1, zva_len, CACHE_LINE_SIZE * 2
- // unroll
+ // count >= L2_SIZE
.p2align 3
-1: st1b_unroll 0, 3
- add tmp2, dst, zva_len
- dc zva, tmp2
- st1b_unroll 4, 7
- add tmp2, tmp2, CACHE_LINE_SIZE
- dc zva, tmp2
- add dst, dst, CACHE_LINE_SIZE * 2
- sub rest, rest, CACHE_LINE_SIZE * 2
- cmp rest, tmp1 // ZF_DIST + CACHE_LINE_SIZE * 2
- b.ge 1b
- cbnz rest, L(unroll8)
- ret
+L(L2):
+ tst valw, 255
+ b.ne L(unroll8)
+ // align dst to CACHE_LINE_SIZE byte boundary
+ and tmp2, dst, CACHE_LINE_SIZE - 1
+ st1b z0.b, p0, [dst, 0, mul vl]
+ st1b z0.b, p0, [dst, 1, mul vl]
+ st1b z0.b, p0, [dst, 2, mul vl]
+ st1b z0.b, p0, [dst, 3, mul vl]
+ sub dst, dst, tmp2
+ add count, count, tmp2
+
+ // clear cachelines using DC ZVA
+ sub count, count, CACHE_LINE_SIZE * 2
+ .p2align 4
+1: add dst, dst, CACHE_LINE_SIZE
+ dc zva, dst
+ subs count, count, CACHE_LINE_SIZE
+ b.hi 1b
+ add count, count, CACHE_LINE_SIZE
+ add dst, dst, CACHE_LINE_SIZE
+ b L(last)
END (MEMSET)
libc_hidden_builtin_def (MEMSET)