175 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * xor.c : Multiple Devices driver for Linux4 *5 * Copyright (C) 1996, 1997, 1998, 1999, 2000,6 * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.7 *8 * Dispatch optimized RAID-5 checksumming functions.9 */10 11#define BH_TRACE 012#include <linux/module.h>13#include <linux/gfp.h>14#include <linux/raid/xor.h>15#include <linux/jiffies.h>16#include <linux/preempt.h>17#include <asm/xor.h>18 19#ifndef XOR_SELECT_TEMPLATE20#define XOR_SELECT_TEMPLATE(x) (x)21#endif22 23/* The xor routines to use. */24static struct xor_block_template *active_template;25 26void27xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)28{29 unsigned long *p1, *p2, *p3, *p4;30 31 p1 = (unsigned long *) srcs[0];32 if (src_count == 1) {33 active_template->do_2(bytes, dest, p1);34 return;35 }36 37 p2 = (unsigned long *) srcs[1];38 if (src_count == 2) {39 active_template->do_3(bytes, dest, p1, p2);40 return;41 }42 43 p3 = (unsigned long *) srcs[2];44 if (src_count == 3) {45 active_template->do_4(bytes, dest, p1, p2, p3);46 return;47 }48 49 p4 = (unsigned long *) srcs[3];50 active_template->do_5(bytes, dest, p1, p2, p3, p4);51}52EXPORT_SYMBOL(xor_blocks);53 54/* Set of all registered templates. */55static struct xor_block_template *__initdata template_list;56 57#ifndef MODULE58static void __init do_xor_register(struct xor_block_template *tmpl)59{60 tmpl->next = template_list;61 template_list = tmpl;62}63 64static int __init register_xor_blocks(void)65{66 active_template = XOR_SELECT_TEMPLATE(NULL);67 68 if (!active_template) {69#define xor_speed do_xor_register70 // register all the templates and pick the first as the default71 XOR_TRY_TEMPLATES;72#undef xor_speed73 active_template = template_list;74 }75 return 0;76}77#endif78 79#define BENCH_SIZE 409680#define REPS 800U81 82static void __init83do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)84{85 int speed;86 unsigned long reps;87 ktime_t min, start, t0;88 89 tmpl->next = template_list;90 template_list = tmpl;91 92 preempt_disable();93 94 reps = 0;95 t0 = ktime_get();96 /* delay start until time has advanced */97 while ((start = ktime_get()) == t0)98 cpu_relax();99 do {100 mb(); /* prevent loop optimization */101 tmpl->do_2(BENCH_SIZE, b1, b2);102 mb();103 } while (reps++ < REPS || (t0 = ktime_get()) == start);104 min = ktime_sub(t0, start);105 106 preempt_enable();107 108 // bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]109 speed = (1000 * reps * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);110 tmpl->speed = speed;111 112 pr_info(" %-16s: %5d MB/sec\n", tmpl->name, speed);113}114 115static int __init116calibrate_xor_blocks(void)117{118 void *b1, *b2;119 struct xor_block_template *f, *fastest;120 121 fastest = XOR_SELECT_TEMPLATE(NULL);122 123 if (fastest) {124 printk(KERN_INFO "xor: automatically using best "125 "checksumming function %-10s\n",126 fastest->name);127 goto out;128 }129 130 b1 = (void *) __get_free_pages(GFP_KERNEL, 2);131 if (!b1) {132 printk(KERN_WARNING "xor: Yikes! No memory available.\n");133 return -ENOMEM;134 }135 b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;136 137 /*138 * If this arch/cpu has a short-circuited selection, don't loop through139 * all the possible functions, just test the best one140 */141 142#define xor_speed(templ) do_xor_speed((templ), b1, b2)143 144 printk(KERN_INFO "xor: measuring software checksum speed\n");145 template_list = NULL;146 XOR_TRY_TEMPLATES;147 fastest = template_list;148 for (f = fastest; f; f = f->next)149 if (f->speed > fastest->speed)150 fastest = f;151 152 pr_info("xor: using function: %s (%d MB/sec)\n",153 fastest->name, fastest->speed);154 155#undef xor_speed156 157 free_pages((unsigned long)b1, 2);158out:159 active_template = fastest;160 return 0;161}162 163static __exit void xor_exit(void) { }164 165MODULE_DESCRIPTION("RAID-5 checksumming functions");166MODULE_LICENSE("GPL");167 168#ifndef MODULE169/* when built-in xor.o must initialize before drivers/md/md.o */170core_initcall(register_xor_blocks);171#endif172 173module_init(calibrate_xor_blocks);174module_exit(xor_exit);175