From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Lingyan Huang <huanglingyan2@huawei.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3] arm64: lib: accelerate do_csum with NEON instruction
Date: Sun, 6 Jan 2019 09:26:39 +0100 [thread overview]
Message-ID: <CAKv+Gu_wsK1UNXSp=5Hvd7XCHKC3cVkYjTYHhvqM4Xt09A9iKg@mail.gmail.com> (raw)
In-Reply-To: <1546739729-17234-1-git-send-email-huanglingyan2@huawei.com>
On Sun, 6 Jan 2019 at 02:56, Lingyan Huang <huanglingyan2@huawei.com> wrote:
>
> Function do_csum() in lib/checksum.c is used to compute checksum,
> which is turned out to be slowly and costs a lot of resources.
> Let's use neon instructions to accelerate the checksum computation
> for arm64.
>
> ------
> V2 ==> V3:
> only modify the arm64 codes instead of modifying headers
> under asm-generic and code in lib/checksum.c.
> ------
> ------
> V1 ==> V2:
> Change NEON assembly code to NEON intrinsic code which is built
> on top of arm_neon.h to avoid dropping into assembly.
> ------
>
Please put the changelog between the --- below and the diffstat
> Here is the comparison results of function ip_compute_csum() between
> general do_csum() and neon instruction do_csum(). The test platform
> is HUAWEI 1620 server with TAISHAN cores.
>
> len(1000cycle) general(ns) do_csum_neon(ns)
> 64B: 58060 59460
> 128B: 82930 83930
> 256B: 132480 73570
> 512B: 230100 86230
> 1024B: 426600 98200
>
Again, very nice performance. How did you test for correctness?
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: Lingyan Huang <huanglingyan2@huawei.com>
> ---
> arch/arm64/include/asm/checksum.h | 5 ++
> arch/arm64/lib/Makefile | 8 +--
> arch/arm64/lib/checksum.c | 26 ++++++++
> arch/arm64/lib/do_csum.c | 136 ++++++++++++++++++++++++++++++++++++++
> 4 files changed, 171 insertions(+), 4 deletions(-)
> create mode 100644 arch/arm64/lib/checksum.c
> create mode 100644 arch/arm64/lib/do_csum.c
>
> diff --git a/arch/arm64/include/asm/checksum.h b/arch/arm64/include/asm/checksum.h
> index 0b6f5a7..7acd713 100644
> --- a/arch/arm64/include/asm/checksum.h
> +++ b/arch/arm64/include/asm/checksum.h
> @@ -26,6 +26,10 @@ static inline __sum16 csum_fold(__wsum csum)
> }
> #define csum_fold csum_fold
>
> +#define do_csum do_csum
> +unsigned int do_csum(const unsigned char *buff, int len);
> +extern unsigned int do_csum_arm(const unsigned char *buff, int len);
> +
> static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
> {
> __uint128_t tmp;
> @@ -46,6 +50,7 @@ static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
> }
> #define ip_fast_csum ip_fast_csum
>
> +
Drop this whitespace-only change
> #include <asm-generic/checksum.h>
>
> #endif /* __ASM_CHECKSUM_H */
> diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
> index 5540a16..c0b5b8c 100644
> --- a/arch/arm64/lib/Makefile
> +++ b/arch/arm64/lib/Makefile
> @@ -3,12 +3,12 @@ lib-y := clear_user.o delay.o copy_from_user.o \
> copy_to_user.o copy_in_user.o copy_page.o \
> clear_page.o memchr.o memcpy.o memmove.o memset.o \
> memcmp.o strcmp.o strncmp.o strlen.o strnlen.o \
> - strchr.o strrchr.o tishift.o
> + strchr.o strrchr.o tishift.o checksum.o
>
> ifeq ($(CONFIG_KERNEL_MODE_NEON), y)
> -obj-$(CONFIG_XOR_BLOCKS) += xor-neon.o
> -CFLAGS_REMOVE_xor-neon.o += -mgeneral-regs-only
> -CFLAGS_xor-neon.o += -ffreestanding
> +obj-y += do_csum.o
Please indent aligned with the others
> +CFLAGS_REMOVE_do_csum.o += -mgeneral-regs-only
> +CFLAGS_do_csum.o += -ffreestanding
> endif
>
> # Tell the compiler to treat all general purpose registers (with the
> diff --git a/arch/arm64/lib/checksum.c b/arch/arm64/lib/checksum.c
> new file mode 100644
> index 0000000..15a31bb
> --- /dev/null
> +++ b/arch/arm64/lib/checksum.c
> @@ -0,0 +1,26 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + *
> + * Authors: Lingyan Huang <huanglingyan2@huawei.com>
> + * Copyright (C) 2018 Hisilicon, Inc. All Rights Reserved.
> + *
> + * Generic C or neon implementation of do_csum operations.
> + * Choose faster neon instructions when NEON is supported.
> + *
> + */
> +
> +#include <asm/neon.h>
> +#include <asm/simd.h>
> +#include <asm/checksum.h>
> +
> +#define CSUM_NEON_THRESHOLD 128
> +
> +unsigned int do_csum(const unsigned char *buff, int len)
> +{
> +#ifdef CONFIG_KERNEL_MODE_NEON
> + if (len >= CSUM_NEON_THRESHOLD)
Please change this into
if (IS_ENABLED(CONFIG_KERNEL_MODE_NEON) &&
len >= CSUM_NEON_THRESHOLD &&
may_use_simd()) {
kernel_neon_begin();
res = do_csum_neon(buff, len);
kernel_neon_end();
}
and drop the intermediate do_csum_arm()
> + return do_csum_arm(buff, len);
> +#endif /* CONFIG_KERNEL_MODE_NEON */
No else? What happens if len < CSUM_NEON_THRESHOLD ?
> +#undef do_csum
Can we drop this?
> + return 0;
> +}
> diff --git a/arch/arm64/lib/do_csum.c b/arch/arm64/lib/do_csum.c
> new file mode 100644
> index 0000000..893583f
> --- /dev/null
> +++ b/arch/arm64/lib/do_csum.c
> @@ -0,0 +1,136 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Authors: Lingyan Huang <huanglingyan2@huawei.com>
> + * Copyright (C) 2018 Hisilicon, Inc. All Rights Reserved.
> + *
> + * Generic C or neon implementation of do_csum operations.
> + * Choose faster neon instructions when NEON is supported.
> + *
> + */
> +
> +#include <asm/neon.h>
> +#include <asm/simd.h>
> +#include <asm/checksum.h>
> +#include <asm/byteorder.h>
> +#include <asm/neon-intrinsics.h>
> +
> +#define CSUM_NEON_THRESHOLD 128
Drop this - it is not used in this file
> +#ifdef CONFIG_KERNEL_MODE_NEON
This file is only built if KERNEL_MODE_NEON=y so the #ifdef can be dropped
> +static inline u32 from64to16(u64 x)
> +{
> + /* add up 32-bit and 32-bit for 32+c bit */
> + x = (x & 0xffffffff) + (x >> 32);
> + /* add up carry.. */
> + x = (x & 0xffffffff) + (x >> 32);
> + /* add up 16-bit and 16-bit for 16+c bit */
> + x = ((u32)x & 0xffff) + ((u32)x >> 16);
> + /* add up carry.. */
> + x = ((u32)x & 0xffff) + ((u32)x >> 16);
> + return x;
> +}
> +
> +unsigned int do_csum_neon(const unsigned char *buff, int len)
> +{
> + unsigned int odd, count;
> + uint64_t result = 0;
> + unsigned int count64;
> + uint32x4_t vzero = (uint32x4_t){0, 0, 0, 0};
> +
> + register uint32x4_t v0, v1, v2, v3;
> +
> + if (unlikely(len <= 0))
> + return result;
> +
> + odd = 1 & (unsigned long)buff;
> + if (unlikely(odd)) {
> + result = *buff;
> + len--;
> + buff++;
> + }
> +
> + count = len >> 1;
> + if (count) {
> + if (2 & (unsigned long)buff) {
> + result += *(unsigned short *)buff;
> + count--;
> + len -= 2;
> + buff += 2;
> + }
> + count >>= 1; /* nr of 32-bit words.. */
> + if (count) {
> + if (4 & (unsigned long)buff) {
> + result += *(unsigned int *)buff;
> + count--;
> + len -= 4;
> + buff += 4;
> + }
> + count >>= 1; /* nr of 64-bit words.. */
> +
> + v0 = vzero;
> + v1 = vzero;
> + v2 = vzero;
> + v3 = vzero;
> +
> + count64 = count >> 3; /* compute 64 Byte circle */
> + while (count64) {
> + v0 = vpadalq_u16(v0,
> + vld1q_u16((uint16_t *)buff + 0));
> + v1 = vpadalq_u16(v1,
> + vld1q_u16((uint16_t *)buff + 8));
> + v2 = vpadalq_u16(v2,
> + vld1q_u16((uint16_t *)buff + 16));
> + v3 = vpadalq_u16(v3,
> + vld1q_u16((uint16_t *)buff + 24));
> + buff += 64;
> + count64--;
> + }
> + v0 = vaddq_u32(v0, v1);
> + v2 = vaddq_u32(v2, v3);
> + v0 = vaddq_u32(v0, v2);
> +
> + count %= 8;
> + while (count >= 2) { /* compute 16 byte circle */
> + v0 = vpadalq_u16(v0,
> + vld1q_u16((uint16_t *)buff + 0));
> + buff += 16;
> + count -= 2;
> + }
> +
> + result += vgetq_lane_u32(v0, 0);
> + result += vgetq_lane_u32(v0, 1);
> + result += vgetq_lane_u32(v0, 2);
> + result += vgetq_lane_u32(v0, 3);
> + if (count & 1) {
> + result += *(unsigned long long *)buff;
> + buff += 8;
> + }
> + if (len & 4) {
> + result += *(unsigned int *)buff;
> + buff += 4;
> + }
> + }
> + if (len & 2) {
> + result += *(unsigned short *)buff;
> + buff += 2;
> + }
> + }
> + if (len & 1)
> + result += *buff;
> + result = from64to16(result);
> + if (odd)
> + result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
> + return result;
> +}
> +#endif
> +
> +
> +unsigned int do_csum_arm(const unsigned char *buff, int len)
> +{
> + unsigned int res;
> +
> + kernel_neon_begin();
> + res = do_csum_neon(buff, len);
> + kernel_neon_end();
> + return res;
> +}
As I said above, please drop this intermediate function and fold the
logic into do_csum()
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next prev parent reply other threads:[~2019-01-06 8:27 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-06 1:55 [PATCH v3] arm64: lib: accelerate do_csum with NEON instruction Lingyan Huang
2019-01-06 8:26 ` Ard Biesheuvel [this message]
[not found] ` <9129b882-60f3-8046-0cb9-e0b2452a118d@huawei.com>
2019-01-08 13:54 ` Will Deacon
2019-01-09 2:03 ` huanglingyan (A)
2019-01-10 4:08 ` 胡海
2019-01-10 8:14 ` huanglingyan (A)
2019-01-16 16:46 ` Will Deacon
2019-01-18 1:07 ` huanglingyan (A)
2019-01-18 11:14 ` Ard Biesheuvel
2019-02-12 2:26 ` huanglingyan (A)
2019-02-12 7:07 ` Ard Biesheuvel
2019-02-13 8:42 ` huanglingyan (A)
2019-02-13 9:15 ` Ard Biesheuvel
2019-02-13 17:55 ` Ard Biesheuvel
2019-02-14 9:57 ` huanglingyan (A)
2019-02-18 8:49 ` huanglingyan (A)
2019-02-18 9:03 ` Ard Biesheuvel
2019-01-09 14:58 ` Dave Martin
2019-01-10 8:03 ` huanglingyan (A)
2019-01-10 13:53 ` Dave Martin
[not found] <1f065749-6676-6489-14ae-fdcfeeb3389c@huawei.com>
2019-01-07 6:11 ` huanglingyan (A)
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