From 63b6b106702e58cdc333a4e59ff35e46dd919ee7 Mon Sep 17 00:00:00 2001 From: Felix Fietkau Date: Sun, 6 Sep 2020 13:28:59 +0200 Subject: [PATCH] kernel: backport improved checksum function for ARM64 Improves network performance in some cases when checksum offload is not available Signed-off-by: Felix Fietkau --- ...Implement-optimised-checksum-routine.patch | 176 ++++++++++++++++++ ...m-Fix-pathological-zero-length-calls.patch | 28 +++ 2 files changed, 204 insertions(+) create mode 100644 target/linux/generic/backport-5.4/041-v5.5-arm64-Implement-optimised-checksum-routine.patch create mode 100644 target/linux/generic/backport-5.4/042-v5.5-arm64-csum-Fix-pathological-zero-length-calls.patch diff --git a/target/linux/generic/backport-5.4/041-v5.5-arm64-Implement-optimised-checksum-routine.patch b/target/linux/generic/backport-5.4/041-v5.5-arm64-Implement-optimised-checksum-routine.patch new file mode 100644 index 0000000000..00ec7d0207 --- /dev/null +++ b/target/linux/generic/backport-5.4/041-v5.5-arm64-Implement-optimised-checksum-routine.patch @@ -0,0 +1,176 @@ +From: Robin Murphy +Date: Wed, 15 Jan 2020 16:42:39 +0000 +Subject: [PATCH] arm64: Implement optimised checksum routine + +Apparently there exist certain workloads which rely heavily on software +checksumming, for which the generic do_csum() implementation becomes a +significant bottleneck. Therefore let's give arm64 its own optimised +version - for ease of maintenance this foregoes assembly or intrisics, +and is thus not actually arm64-specific, but does rely heavily on C +idioms that translate well to the A64 ISA and the typical load/store +capabilities of most ARMv8 CPU cores. + +The resulting increase in checksum throughput scales nicely with buffer +size, tending towards 4x for a small in-order core (Cortex-A53), and up +to 6x or more for an aggressive big core (Ampere eMAG). + +Reported-by: Lingyan Huang +Tested-by: Lingyan Huang +Signed-off-by: Robin Murphy +Signed-off-by: Will Deacon +--- + create mode 100644 arch/arm64/lib/csum.c + +--- a/arch/arm64/include/asm/checksum.h ++++ b/arch/arm64/include/asm/checksum.h +@@ -36,6 +36,9 @@ static inline __sum16 ip_fast_csum(const + } + #define ip_fast_csum ip_fast_csum + ++extern unsigned int do_csum(const unsigned char *buff, int len); ++#define do_csum do_csum ++ + #include + + #endif /* __ASM_CHECKSUM_H */ +--- a/arch/arm64/lib/Makefile ++++ b/arch/arm64/lib/Makefile +@@ -1,9 +1,9 @@ + # SPDX-License-Identifier: GPL-2.0 + 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 ++ clear_page.o csum.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 + + ifeq ($(CONFIG_KERNEL_MODE_NEON), y) + obj-$(CONFIG_XOR_BLOCKS) += xor-neon.o +--- /dev/null ++++ b/arch/arm64/lib/csum.c +@@ -0,0 +1,123 @@ ++// SPDX-License-Identifier: GPL-2.0-only ++// Copyright (C) 2019-2020 Arm Ltd. ++ ++#include ++#include ++#include ++ ++#include ++ ++/* Looks dumb, but generates nice-ish code */ ++static u64 accumulate(u64 sum, u64 data) ++{ ++ __uint128_t tmp = (__uint128_t)sum + data; ++ return tmp + (tmp >> 64); ++} ++ ++unsigned int do_csum(const unsigned char *buff, int len) ++{ ++ unsigned int offset, shift, sum; ++ const u64 *ptr; ++ u64 data, sum64 = 0; ++ ++ offset = (unsigned long)buff & 7; ++ /* ++ * This is to all intents and purposes safe, since rounding down cannot ++ * result in a different page or cache line being accessed, and @buff ++ * should absolutely not be pointing to anything read-sensitive. We do, ++ * however, have to be careful not to piss off KASAN, which means using ++ * unchecked reads to accommodate the head and tail, for which we'll ++ * compensate with an explicit check up-front. ++ */ ++ kasan_check_read(buff, len); ++ ptr = (u64 *)(buff - offset); ++ len = len + offset - 8; ++ ++ /* ++ * Head: zero out any excess leading bytes. Shifting back by the same ++ * amount should be at least as fast as any other way of handling the ++ * odd/even alignment, and means we can ignore it until the very end. ++ */ ++ shift = offset * 8; ++ data = READ_ONCE_NOCHECK(*ptr++); ++#ifdef __LITTLE_ENDIAN ++ data = (data >> shift) << shift; ++#else ++ data = (data << shift) >> shift; ++#endif ++ ++ /* ++ * Body: straightforward aligned loads from here on (the paired loads ++ * underlying the quadword type still only need dword alignment). The ++ * main loop strictly excludes the tail, so the second loop will always ++ * run at least once. ++ */ ++ while (unlikely(len > 64)) { ++ __uint128_t tmp1, tmp2, tmp3, tmp4; ++ ++ tmp1 = READ_ONCE_NOCHECK(*(__uint128_t *)ptr); ++ tmp2 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 2)); ++ tmp3 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 4)); ++ tmp4 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 6)); ++ ++ len -= 64; ++ ptr += 8; ++ ++ /* This is the "don't dump the carry flag into a GPR" idiom */ ++ tmp1 += (tmp1 >> 64) | (tmp1 << 64); ++ tmp2 += (tmp2 >> 64) | (tmp2 << 64); ++ tmp3 += (tmp3 >> 64) | (tmp3 << 64); ++ tmp4 += (tmp4 >> 64) | (tmp4 << 64); ++ tmp1 = ((tmp1 >> 64) << 64) | (tmp2 >> 64); ++ tmp1 += (tmp1 >> 64) | (tmp1 << 64); ++ tmp3 = ((tmp3 >> 64) << 64) | (tmp4 >> 64); ++ tmp3 += (tmp3 >> 64) | (tmp3 << 64); ++ tmp1 = ((tmp1 >> 64) << 64) | (tmp3 >> 64); ++ tmp1 += (tmp1 >> 64) | (tmp1 << 64); ++ tmp1 = ((tmp1 >> 64) << 64) | sum64; ++ tmp1 += (tmp1 >> 64) | (tmp1 << 64); ++ sum64 = tmp1 >> 64; ++ } ++ while (len > 8) { ++ __uint128_t tmp; ++ ++ sum64 = accumulate(sum64, data); ++ tmp = READ_ONCE_NOCHECK(*(__uint128_t *)ptr); ++ ++ len -= 16; ++ ptr += 2; ++ ++#ifdef __LITTLE_ENDIAN ++ data = tmp >> 64; ++ sum64 = accumulate(sum64, tmp); ++#else ++ data = tmp; ++ sum64 = accumulate(sum64, tmp >> 64); ++#endif ++ } ++ if (len > 0) { ++ sum64 = accumulate(sum64, data); ++ data = READ_ONCE_NOCHECK(*ptr); ++ len -= 8; ++ } ++ /* ++ * Tail: zero any over-read bytes similarly to the head, again ++ * preserving odd/even alignment. ++ */ ++ shift = len * -8; ++#ifdef __LITTLE_ENDIAN ++ data = (data << shift) >> shift; ++#else ++ data = (data >> shift) << shift; ++#endif ++ sum64 = accumulate(sum64, data); ++ ++ /* Finally, folding */ ++ sum64 += (sum64 >> 32) | (sum64 << 32); ++ sum = sum64 >> 32; ++ sum += (sum >> 16) | (sum << 16); ++ if (offset & 1) ++ return (u16)swab32(sum); ++ ++ return sum >> 16; ++} diff --git a/target/linux/generic/backport-5.4/042-v5.5-arm64-csum-Fix-pathological-zero-length-calls.patch b/target/linux/generic/backport-5.4/042-v5.5-arm64-csum-Fix-pathological-zero-length-calls.patch new file mode 100644 index 0000000000..50b210e14f --- /dev/null +++ b/target/linux/generic/backport-5.4/042-v5.5-arm64-csum-Fix-pathological-zero-length-calls.patch @@ -0,0 +1,28 @@ +From: Robin Murphy +Date: Fri, 17 Jan 2020 15:48:39 +0000 +Subject: [PATCH] arm64: csum: Fix pathological zero-length calls + +In validating the checksumming results of the new routine, I sadly +neglected to test its not-checksumming results. Thus it slipped through +that the one case where @buff is already dword-aligned and @len = 0 +manages to defeat the tail-masking logic and behave as if @len = 8. +For a zero length it doesn't make much sense to deference @buff anyway, +so just add an early return (which has essentially zero impact on +performance). + +Signed-off-by: Robin Murphy +Signed-off-by: Will Deacon +--- + +--- a/arch/arm64/lib/csum.c ++++ b/arch/arm64/lib/csum.c +@@ -20,6 +20,9 @@ unsigned int do_csum(const unsigned char + const u64 *ptr; + u64 data, sum64 = 0; + ++ if (unlikely(len == 0)) ++ return 0; ++ + offset = (unsigned long)buff & 7; + /* + * This is to all intents and purposes safe, since rounding down cannot -- 2.30.2