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riscv: optimized memcpy
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 <mcroce@microsoft.com> Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
This commit is contained in:
Matteo Croce
Emil Renner Berthing
parent
4ec5183ec4
commit
af5a304a0b
6 changed files with 104 additions and 116 deletions
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@ -12,9 +12,11 @@
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#define __HAVE_ARCH_MEMSET
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extern asmlinkage void *memset(void *, int, size_t);
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extern asmlinkage void *__memset(void *, int, size_t);
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#define __HAVE_ARCH_MEMCPY
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extern asmlinkage void *memcpy(void *, const void *, size_t);
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extern asmlinkage void *__memcpy(void *, const void *, size_t);
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extern void *memcpy(void *dest, const void *src, size_t count);
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extern void *__memcpy(void *dest, const void *src, size_t count);
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#define __HAVE_ARCH_MEMMOVE
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extern asmlinkage void *memmove(void *, const void *, size_t);
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extern asmlinkage void *__memmove(void *, const void *, size_t);
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@ -10,8 +10,6 @@
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* Assembly functions that may be used (directly or indirectly) by modules
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*/
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EXPORT_SYMBOL(memset);
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EXPORT_SYMBOL(memcpy);
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EXPORT_SYMBOL(memmove);
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EXPORT_SYMBOL(__memset);
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EXPORT_SYMBOL(__memcpy);
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EXPORT_SYMBOL(__memmove);
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@ -1,9 +1,14 @@
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# SPDX-License-Identifier: GPL-2.0-only
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lib-y += delay.o
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lib-y += memcpy.o
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lib-y += memset.o
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lib-y += memmove.o
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lib-$(CONFIG_MMU) += uaccess.o
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lib-$(CONFIG_64BIT) += tishift.o
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lib-y += string.o
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# string.o implements standard library functions like memset/memcpy etc.
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# Use -ffreestanding to ensure that the compiler does not try to "optimize"
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# them into calls to themselves.
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CFLAGS_string.o := -ffreestanding
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obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
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@ -1,108 +0,0 @@
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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2013 Regents of the University of California
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*/
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#include <linux/linkage.h>
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#include <asm/asm.h>
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/* void *memcpy(void *, const void *, size_t) */
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ENTRY(__memcpy)
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WEAK(memcpy)
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move t6, a0 /* Preserve return value */
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/* Defer to byte-oriented copy for small sizes */
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sltiu a3, a2, 128
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bnez a3, 4f
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/* Use word-oriented copy only if low-order bits match */
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andi a3, t6, SZREG-1
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andi a4, a1, SZREG-1
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bne a3, a4, 4f
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beqz a3, 2f /* Skip if already aligned */
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/*
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* Round to nearest double word-aligned address
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* greater than or equal to start address
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*/
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andi a3, a1, ~(SZREG-1)
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addi a3, a3, SZREG
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/* Handle initial misalignment */
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sub a4, a3, a1
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1:
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lb a5, 0(a1)
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addi a1, a1, 1
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sb a5, 0(t6)
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addi t6, t6, 1
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bltu a1, a3, 1b
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sub a2, a2, a4 /* Update count */
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2:
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andi a4, a2, ~((16*SZREG)-1)
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beqz a4, 4f
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add a3, a1, a4
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3:
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REG_L a4, 0(a1)
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REG_L a5, SZREG(a1)
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REG_L a6, 2*SZREG(a1)
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REG_L a7, 3*SZREG(a1)
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REG_L t0, 4*SZREG(a1)
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REG_L t1, 5*SZREG(a1)
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REG_L t2, 6*SZREG(a1)
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REG_L t3, 7*SZREG(a1)
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REG_L t4, 8*SZREG(a1)
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REG_L t5, 9*SZREG(a1)
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REG_S a4, 0(t6)
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REG_S a5, SZREG(t6)
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REG_S a6, 2*SZREG(t6)
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REG_S a7, 3*SZREG(t6)
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REG_S t0, 4*SZREG(t6)
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REG_S t1, 5*SZREG(t6)
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REG_S t2, 6*SZREG(t6)
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REG_S t3, 7*SZREG(t6)
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REG_S t4, 8*SZREG(t6)
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REG_S t5, 9*SZREG(t6)
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REG_L a4, 10*SZREG(a1)
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REG_L a5, 11*SZREG(a1)
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REG_L a6, 12*SZREG(a1)
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REG_L a7, 13*SZREG(a1)
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REG_L t0, 14*SZREG(a1)
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REG_L t1, 15*SZREG(a1)
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addi a1, a1, 16*SZREG
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REG_S a4, 10*SZREG(t6)
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REG_S a5, 11*SZREG(t6)
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REG_S a6, 12*SZREG(t6)
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REG_S a7, 13*SZREG(t6)
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REG_S t0, 14*SZREG(t6)
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REG_S t1, 15*SZREG(t6)
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addi t6, t6, 16*SZREG
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bltu a1, a3, 3b
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andi a2, a2, (16*SZREG)-1 /* Update count */
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4:
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/* Handle trailing misalignment */
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beqz a2, 6f
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add a3, a1, a2
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/* Use word-oriented copy if co-aligned to word boundary */
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or a5, a1, t6
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or a5, a5, a3
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andi a5, a5, 3
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bnez a5, 5f
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7:
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lw a4, 0(a1)
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addi a1, a1, 4
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sw a4, 0(t6)
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addi t6, t6, 4
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bltu a1, a3, 7b
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ret
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5:
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lb a4, 0(a1)
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addi a1, a1, 1
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sb a4, 0(t6)
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addi t6, t6, 1
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bltu a1, a3, 5b
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6:
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ret
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END(__memcpy)
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91
arch/riscv/lib/string.c
Normal file
91
arch/riscv/lib/string.c
Normal file
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@ -0,0 +1,91 @@
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* String functions optimized for hardware which doesn't
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* handle unaligned memory accesses efficiently.
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*
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* Copyright (C) 2021 Matteo Croce
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*/
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#define __NO_FORTIFY
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#include <linux/types.h>
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#include <linux/module.h>
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/* Minimum size for a word copy to be convenient */
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#define BYTES_LONG sizeof(long)
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#define WORD_MASK (BYTES_LONG - 1)
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#define MIN_THRESHOLD (BYTES_LONG * 2)
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/* convenience union to avoid cast between different pointer types */
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union types {
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u8 *as_u8;
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unsigned long *as_ulong;
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uintptr_t as_uptr;
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};
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union const_types {
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const u8 *as_u8;
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unsigned long *as_ulong;
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uintptr_t as_uptr;
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};
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void *__memcpy(void *dest, const void *src, size_t count)
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{
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union const_types s = { .as_u8 = src };
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union types d = { .as_u8 = dest };
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int distance = 0;
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if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
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if (count < MIN_THRESHOLD)
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goto copy_remainder;
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/* Copy a byte at time until destination is aligned. */
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for (; d.as_uptr & WORD_MASK; count--)
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*d.as_u8++ = *s.as_u8++;
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distance = s.as_uptr & WORD_MASK;
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}
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if (distance) {
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unsigned long last, next;
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/*
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* s is distance bytes ahead of d, and d just reached
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* the alignment boundary. Move s backward to word align it
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* and shift data to compensate for distance, in order to do
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* word-by-word copy.
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*/
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s.as_u8 -= distance;
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next = s.as_ulong[0];
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for (; count >= BYTES_LONG; count -= BYTES_LONG) {
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last = next;
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next = s.as_ulong[1];
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d.as_ulong[0] = last >> (distance * 8) |
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next << ((BYTES_LONG - distance) * 8);
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d.as_ulong++;
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s.as_ulong++;
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}
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/* Restore s with the original offset. */
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s.as_u8 += distance;
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} else {
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/*
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* If the source and dest lower bits are the same, do a simple
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* 32/64 bit wide copy.
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*/
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for (; count >= BYTES_LONG; count -= BYTES_LONG)
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*d.as_ulong++ = *s.as_ulong++;
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}
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copy_remainder:
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while (count--)
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*d.as_u8++ = *s.as_u8++;
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return dest;
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}
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EXPORT_SYMBOL(__memcpy);
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void *memcpy(void *dest, const void *src, size_t count) __weak __alias(__memcpy);
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EXPORT_SYMBOL(memcpy);
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@ -1,7 +1,7 @@
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# SPDX-License-Identifier: GPL-2.0
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OBJECT_FILES_NON_STANDARD := y
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purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o
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purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o rvstring.o memset.o
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targets += $(purgatory-y)
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PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
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@ -12,8 +12,8 @@ $(obj)/string.o: $(srctree)/lib/string.c FORCE
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$(obj)/ctype.o: $(srctree)/lib/ctype.c FORCE
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$(call if_changed_rule,cc_o_c)
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$(obj)/memcpy.o: $(srctree)/arch/riscv/lib/memcpy.S FORCE
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$(call if_changed_rule,as_o_S)
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$(obj)/rvstring.o: $(srctree)/arch/riscv/lib/string.c FORCE
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$(call if_changed_rule,cc_o_c)
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$(obj)/memset.o: $(srctree)/arch/riscv/lib/memset.S FORCE
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$(call if_changed_rule,as_o_S)
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