1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * xor.c : Multiple Devices driver for Linux 4 * 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 0 12 #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_TEMPLATE 20 #define XOR_SELECT_TEMPLATE(x) (x) 21 #endif 22 23 /* The xor routines to use. */ 24 static struct xor_block_template *active_template; 25 26 void 27 xor_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 } 52 EXPORT_SYMBOL(xor_blocks); 53 54 /* Set of all registered templates. */ 55 static struct xor_block_template *__initdata template_list; 56 57 #define BENCH_SIZE (PAGE_SIZE) 58 59 static void __init 60 do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2) 61 { 62 int speed; 63 unsigned long now, j; 64 int i, count, max; 65 66 tmpl->next = template_list; 67 template_list = tmpl; 68 69 preempt_disable(); 70 71 /* 72 * Count the number of XORs done during a whole jiffy, and use 73 * this to calculate the speed of checksumming. We use a 2-page 74 * allocation to have guaranteed color L1-cache layout. 75 */ 76 max = 0; 77 for (i = 0; i < 5; i++) { 78 j = jiffies; 79 count = 0; 80 while ((now = jiffies) == j) 81 cpu_relax(); 82 while (time_before(jiffies, now + 1)) { 83 mb(); /* prevent loop optimzation */ 84 tmpl->do_2(BENCH_SIZE, b1, b2); 85 mb(); 86 count++; 87 mb(); 88 } 89 if (count > max) 90 max = count; 91 } 92 93 preempt_enable(); 94 95 speed = max * (HZ * BENCH_SIZE / 1024); 96 tmpl->speed = speed; 97 98 printk(KERN_INFO " %-10s: %5d.%03d MB/sec\n", tmpl->name, 99 speed / 1000, speed % 1000); 100 } 101 102 static int __init 103 calibrate_xor_blocks(void) 104 { 105 void *b1, *b2; 106 struct xor_block_template *f, *fastest; 107 108 fastest = XOR_SELECT_TEMPLATE(NULL); 109 110 if (fastest) { 111 printk(KERN_INFO "xor: automatically using best " 112 "checksumming function %-10s\n", 113 fastest->name); 114 goto out; 115 } 116 117 b1 = (void *) __get_free_pages(GFP_KERNEL, 2); 118 if (!b1) { 119 printk(KERN_WARNING "xor: Yikes! No memory available.\n"); 120 return -ENOMEM; 121 } 122 b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE; 123 124 /* 125 * If this arch/cpu has a short-circuited selection, don't loop through 126 * all the possible functions, just test the best one 127 */ 128 129 #define xor_speed(templ) do_xor_speed((templ), b1, b2) 130 131 printk(KERN_INFO "xor: measuring software checksum speed\n"); 132 XOR_TRY_TEMPLATES; 133 fastest = template_list; 134 for (f = fastest; f; f = f->next) 135 if (f->speed > fastest->speed) 136 fastest = f; 137 138 printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n", 139 fastest->name, fastest->speed / 1000, fastest->speed % 1000); 140 141 #undef xor_speed 142 143 free_pages((unsigned long)b1, 2); 144 out: 145 active_template = fastest; 146 return 0; 147 } 148 149 static __exit void xor_exit(void) { } 150 151 MODULE_LICENSE("GPL"); 152 153 /* when built-in xor.o must initialize before drivers/md/md.o */ 154 core_initcall(calibrate_xor_blocks); 155 module_exit(xor_exit); 156