[PATCH v3] arm64: lib: accelerate do_csum with NEON instruction

[Lingyan Huang <huanglingyan2@huawei.com>]

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.
------

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


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
 
+
 #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
+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)
+		return do_csum_arm(buff, len);
+#endif  /* CONFIG_KERNEL_MODE_NEON */
+#undef do_csum
+	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
+#ifdef CONFIG_KERNEL_MODE_NEON
+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;
+}
+
-- 
2.7.4


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