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[37.119.128.179]) by smtp.gmail.com with ESMTPSA id g11sm4497850edz.12.2021.06.17.08.28.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Jun 2021 08:28:20 -0700 (PDT) From: Matteo Croce To: linux-riscv@lists.infradead.org Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Paul Walmsley , Palmer Dabbelt , Albert Ou , Atish Patra , Emil Renner Berthing , Akira Tsukamoto , Drew Fustini , Bin Meng , David Laight , Guo Ren Subject: [PATCH v3 1/3] riscv: optimized memcpy Date: Thu, 17 Jun 2021 17:27:52 +0200 Message-Id: <20210617152754.17960-2-mcroce@linux.microsoft.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210617152754.17960-1-mcroce@linux.microsoft.com> References: <20210617152754.17960-1-mcroce@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Matteo Croce Write a C version of memcpy() which uses the biggest data size allowed, without generating unaligned accesses. The procedure is made of three steps: First copy data one byte at time until the destination buffer is aligned to a long boundary. Then copy the data one long at time shifting the current and the next u8 to compose a long at every cycle. Finally, copy the remainder one byte at time. On a BeagleV, the TCP RX throughput increased by 45%: before: $ iperf3 -c beaglev Connecting to host beaglev, port 5201 [ 5] local 192.168.85.6 port 44840 connected to 192.168.85.48 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 76.4 MBytes 641 Mbits/sec 27 624 KBytes [ 5] 1.00-2.00 sec 72.5 MBytes 608 Mbits/sec 0 708 KBytes [ 5] 2.00-3.00 sec 73.8 MBytes 619 Mbits/sec 10 451 KBytes [ 5] 3.00-4.00 sec 72.5 MBytes 608 Mbits/sec 0 564 KBytes [ 5] 4.00-5.00 sec 73.8 MBytes 619 Mbits/sec 0 658 KBytes [ 5] 5.00-6.00 sec 73.8 MBytes 619 Mbits/sec 14 522 KBytes [ 5] 6.00-7.00 sec 73.8 MBytes 619 Mbits/sec 0 621 KBytes [ 5] 7.00-8.00 sec 72.5 MBytes 608 Mbits/sec 0 706 KBytes [ 5] 8.00-9.00 sec 73.8 MBytes 619 Mbits/sec 20 580 KBytes [ 5] 9.00-10.00 sec 73.8 MBytes 619 Mbits/sec 0 672 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 736 MBytes 618 Mbits/sec 71 sender [ 5] 0.00-10.01 sec 733 MBytes 615 Mbits/sec receiver after: $ iperf3 -c beaglev Connecting to host beaglev, port 5201 [ 5] local 192.168.85.6 port 44864 connected to 192.168.85.48 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 109 MBytes 912 Mbits/sec 48 559 KBytes [ 5] 1.00-2.00 sec 108 MBytes 902 Mbits/sec 0 690 KBytes [ 5] 2.00-3.00 sec 106 MBytes 891 Mbits/sec 36 396 KBytes [ 5] 3.00-4.00 sec 108 MBytes 902 Mbits/sec 0 567 KBytes [ 5] 4.00-5.00 sec 106 MBytes 891 Mbits/sec 0 699 KBytes [ 5] 5.00-6.00 sec 106 MBytes 891 Mbits/sec 32 414 KBytes [ 5] 6.00-7.00 sec 106 MBytes 891 Mbits/sec 0 583 KBytes [ 5] 7.00-8.00 sec 106 MBytes 891 Mbits/sec 0 708 KBytes [ 5] 8.00-9.00 sec 106 MBytes 891 Mbits/sec 28 433 KBytes [ 5] 9.00-10.00 sec 108 MBytes 902 Mbits/sec 0 591 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 1.04 GBytes 897 Mbits/sec 144 sender [ 5] 0.00-10.01 sec 1.04 GBytes 894 Mbits/sec receiver And the decreased CPU time of the memcpy() is observable with perf top. This is the `perf top -Ue task-clock` output when doing the test: before: Overhead Shared O Symbol 42.22% [kernel] [k] memcpy 35.00% [kernel] [k] __asm_copy_to_user 3.50% [kernel] [k] sifive_l2_flush64_range 2.30% [kernel] [k] stmmac_napi_poll_rx 1.11% [kernel] [k] memset after: Overhead Shared O Symbol 45.69% [kernel] [k] __asm_copy_to_user 29.06% [kernel] [k] memcpy 4.09% [kernel] [k] sifive_l2_flush64_range 2.77% [kernel] [k] stmmac_napi_poll_rx 1.24% [kernel] [k] memset Signed-off-by: Matteo Croce --- arch/riscv/include/asm/string.h | 8 ++- arch/riscv/kernel/riscv_ksyms.c | 2 - arch/riscv/lib/Makefile | 2 +- arch/riscv/lib/memcpy.S | 108 -------------------------------- arch/riscv/lib/string.c | 91 +++++++++++++++++++++++++++ 5 files changed, 98 insertions(+), 113 deletions(-) delete mode 100644 arch/riscv/lib/memcpy.S create mode 100644 arch/riscv/lib/string.c diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h index 909049366555..6b5d6fc3eab4 100644 --- a/arch/riscv/include/asm/string.h +++ b/arch/riscv/include/asm/string.h @@ -12,9 +12,13 @@ #define __HAVE_ARCH_MEMSET extern asmlinkage void *memset(void *, int, size_t); extern asmlinkage void *__memset(void *, int, size_t); + +#ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE #define __HAVE_ARCH_MEMCPY -extern asmlinkage void *memcpy(void *, const void *, size_t); -extern asmlinkage void *__memcpy(void *, const void *, size_t); +extern void *memcpy(void *dest, const void *src, size_t count); +extern void *__memcpy(void *dest, const void *src, size_t count); +#endif + #define __HAVE_ARCH_MEMMOVE extern asmlinkage void *memmove(void *, const void *, size_t); extern asmlinkage void *__memmove(void *, const void *, size_t); diff --git a/arch/riscv/kernel/riscv_ksyms.c b/arch/riscv/kernel/riscv_ksyms.c index 5ab1c7e1a6ed..3f6d512a5b97 100644 --- a/arch/riscv/kernel/riscv_ksyms.c +++ b/arch/riscv/kernel/riscv_ksyms.c @@ -10,8 +10,6 @@ * Assembly functions that may be used (directly or indirectly) by modules */ EXPORT_SYMBOL(memset); -EXPORT_SYMBOL(memcpy); EXPORT_SYMBOL(memmove); EXPORT_SYMBOL(__memset); -EXPORT_SYMBOL(__memcpy); EXPORT_SYMBOL(__memmove); diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile index 25d5c9664e57..2ffe85d4baee 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -1,9 +1,9 @@ # SPDX-License-Identifier: GPL-2.0-only lib-y += delay.o -lib-y += memcpy.o lib-y += memset.o lib-y += memmove.o lib-$(CONFIG_MMU) += uaccess.o lib-$(CONFIG_64BIT) += tishift.o +lib-$(CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE) += string.o obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o diff --git a/arch/riscv/lib/memcpy.S b/arch/riscv/lib/memcpy.S deleted file mode 100644 index 51ab716253fa..000000000000 --- a/arch/riscv/lib/memcpy.S +++ /dev/null @@ -1,108 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0-only */ -/* - * Copyright (C) 2013 Regents of the University of California - */ - -#include -#include - -/* void *memcpy(void *, const void *, size_t) */ -ENTRY(__memcpy) -WEAK(memcpy) - move t6, a0 /* Preserve return value */ - - /* Defer to byte-oriented copy for small sizes */ - sltiu a3, a2, 128 - bnez a3, 4f - /* Use word-oriented copy only if low-order bits match */ - andi a3, t6, SZREG-1 - andi a4, a1, SZREG-1 - bne a3, a4, 4f - - beqz a3, 2f /* Skip if already aligned */ - /* - * Round to nearest double word-aligned address - * greater than or equal to start address - */ - andi a3, a1, ~(SZREG-1) - addi a3, a3, SZREG - /* Handle initial misalignment */ - sub a4, a3, a1 -1: - lb a5, 0(a1) - addi a1, a1, 1 - sb a5, 0(t6) - addi t6, t6, 1 - bltu a1, a3, 1b - sub a2, a2, a4 /* Update count */ - -2: - andi a4, a2, ~((16*SZREG)-1) - beqz a4, 4f - add a3, a1, a4 -3: - REG_L a4, 0(a1) - REG_L a5, SZREG(a1) - REG_L a6, 2*SZREG(a1) - REG_L a7, 3*SZREG(a1) - REG_L t0, 4*SZREG(a1) - REG_L t1, 5*SZREG(a1) - REG_L t2, 6*SZREG(a1) - REG_L t3, 7*SZREG(a1) - REG_L t4, 8*SZREG(a1) - REG_L t5, 9*SZREG(a1) - REG_S a4, 0(t6) - REG_S a5, SZREG(t6) - REG_S a6, 2*SZREG(t6) - REG_S a7, 3*SZREG(t6) - REG_S t0, 4*SZREG(t6) - REG_S t1, 5*SZREG(t6) - REG_S t2, 6*SZREG(t6) - REG_S t3, 7*SZREG(t6) - REG_S t4, 8*SZREG(t6) - REG_S t5, 9*SZREG(t6) - REG_L a4, 10*SZREG(a1) - REG_L a5, 11*SZREG(a1) - REG_L a6, 12*SZREG(a1) - REG_L a7, 13*SZREG(a1) - REG_L t0, 14*SZREG(a1) - REG_L t1, 15*SZREG(a1) - addi a1, a1, 16*SZREG - REG_S a4, 10*SZREG(t6) - REG_S a5, 11*SZREG(t6) - REG_S a6, 12*SZREG(t6) - REG_S a7, 13*SZREG(t6) - REG_S t0, 14*SZREG(t6) - REG_S t1, 15*SZREG(t6) - addi t6, t6, 16*SZREG - bltu a1, a3, 3b - andi a2, a2, (16*SZREG)-1 /* Update count */ - -4: - /* Handle trailing misalignment */ - beqz a2, 6f - add a3, a1, a2 - - /* Use word-oriented copy if co-aligned to word boundary */ - or a5, a1, t6 - or a5, a5, a3 - andi a5, a5, 3 - bnez a5, 5f -7: - lw a4, 0(a1) - addi a1, a1, 4 - sw a4, 0(t6) - addi t6, t6, 4 - bltu a1, a3, 7b - - ret - -5: - lb a4, 0(a1) - addi a1, a1, 1 - sb a4, 0(t6) - addi t6, t6, 1 - bltu a1, a3, 5b -6: - ret -END(__memcpy) diff --git a/arch/riscv/lib/string.c b/arch/riscv/lib/string.c new file mode 100644 index 000000000000..e48a79a045d8 --- /dev/null +++ b/arch/riscv/lib/string.c @@ -0,0 +1,91 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * String functions optimized for hardware which doesn't + * handle unaligned memory accesses efficiently. + * + * Copyright (C) 2021 Matteo Croce + */ + +#include +#include + +/* Minimum size for a word copy to be convenient */ +#define MIN_THRESHOLD (BITS_PER_LONG / 8 * 2) + +/* convenience union to avoid cast between different pointer types */ +union types { + u8 *u8; + unsigned long *ulong; + uintptr_t uptr; +}; + +union const_types { + const u8 *u8; + unsigned long *ulong; +}; + +void *__memcpy(void *dest, const void *src, size_t count) +{ + const int bytes_long = BITS_PER_LONG / 8; +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS + const int mask = bytes_long - 1; + const int distance = (src - dest) & mask; +#endif + union const_types s = { .u8 = src }; + union types d = { .u8 = dest }; + +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS + if (count < MIN_THRESHOLD) + goto copy_remainder; + + /* copy a byte at time until destination is aligned */ + for (; count && d.uptr & mask; count--) + *d.u8++ = *s.u8++; + + if (distance) { + unsigned long last, next; + + /* move s backward to the previous alignment boundary */ + s.u8 -= distance; + + /* 32/64 bit wide copy from s to d. + * d is aligned now but s is not, so read s alignment wise, + * and do proper shift to get the right value. + * Works only on Little Endian machines. + */ + for (next = s.ulong[0]; count >= bytes_long + mask; count -= bytes_long) { + last = next; + next = s.ulong[1]; + + d.ulong[0] = last >> (distance * 8) | + next << ((bytes_long - distance) * 8); + + d.ulong++; + s.ulong++; + } + + /* restore s with the original offset */ + s.u8 += distance; + } else +#endif + { + /* if the source and dest lower bits are the same, do a simple + * 32/64 bit wide copy. + */ + for (; count >= bytes_long; count -= bytes_long) + *d.ulong++ = *s.ulong++; + } + + /* suppress warning when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y */ + goto copy_remainder; + +copy_remainder: + while (count--) + *d.u8++ = *s.u8++; + + return dest; +} +EXPORT_SYMBOL(__memcpy); + +void *memcpy(void *dest, const void *src, size_t count) __weak __alias(__memcpy); +EXPORT_SYMBOL(memcpy); -- 2.31.1