crypto/xor.c

   1 /*
   2  * xor.c : Multiple Devices driver for Linux
   3  *
   4  * Copyright (C) 1996, 1997, 1998, 1999, 2000,
   5  * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
   6  *
   7  * Dispatch optimized RAID-5 checksumming functions.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2, or (at your option)
  12  * any later version.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * (for example /usr/src/linux/COPYING); if not, write to the Free
  16  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #define BH_TRACE 0
  20 #include <linux/module.h>
  21 #include <linux/gfp.h>
  22 #include <linux/raid/xor.h>
  23 #include <linux/jiffies.h>
  24 #include <linux/preempt.h>
  25 #include <asm/xor.h>
  26
  27 #ifndef XOR_SELECT_TEMPLATE
  28 #define XOR_SELECT_TEMPLATE(x) (x)
  29 #endif
  30
  31 /* The xor routines to use.  */
  32 static struct xor_block_template *active_template;
  33
  34 void
  35 xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
  36 {
  37         unsigned long *p1, *p2, *p3, *p4;
  38
  39         p1 = (unsigned long *) srcs[0];
  40         if (src_count == 1) {
  41                 active_template->do_2(bytes, dest, p1);
  42                 return;
  43         }
  44
  45         p2 = (unsigned long *) srcs[1];
  46         if (src_count == 2) {
  47                 active_template->do_3(bytes, dest, p1, p2);
  48                 return;
  49         }
  50
  51         p3 = (unsigned long *) srcs[2];
  52         if (src_count == 3) {
  53                 active_template->do_4(bytes, dest, p1, p2, p3);
  54                 return;
  55         }
  56
  57         p4 = (unsigned long *) srcs[3];
  58         active_template->do_5(bytes, dest, p1, p2, p3, p4);
  59 }
  60 EXPORT_SYMBOL(xor_blocks);
  61
  62 /* Set of all registered templates.  */
  63 static struct xor_block_template *__initdata template_list;
  64
  65 #define BENCH_SIZE (PAGE_SIZE)
  66
  67 static void __init
  68 do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
  69 {
  70         int speed;
  71         unsigned long now, j;
  72         int i, count, max;
  73
  74         tmpl->next = template_list;
  75         template_list = tmpl;
  76
  77         preempt_disable();
  78
  79         /*
  80          * Count the number of XORs done during a whole jiffy, and use
  81          * this to calculate the speed of checksumming.  We use a 2-page
  82          * allocation to have guaranteed color L1-cache layout.
  83          */
  84         max = 0;
  85         for (i = 0; i < 5; i++) {
  86                 j = jiffies;
  87                 count = 0;
  88                 while ((now = jiffies) == j)
  89                         cpu_relax();
  90                 while (time_before(jiffies, now + 1)) {
  91                         mb(); /* prevent loop optimzation */
  92                         tmpl->do_2(BENCH_SIZE, b1, b2);
  93                         mb();
  94                         count++;
  95                         mb();
  96                 }
  97                 if (count > max)
  98                         max = count;
  99         }
 100
 101         preempt_enable();
 102
 103         speed = max * (HZ * BENCH_SIZE / 1024);
 104         tmpl->speed = speed;
 105
 106         printk(KERN_INFO "   %-10s: %5d.%03d MB/sec\n", tmpl->name,
 107                speed / 1000, speed % 1000);
 108 }
 109
 110 static int __init
 111 calibrate_xor_blocks(void)
 112 {
 113         void *b1, *b2;
 114         struct xor_block_template *f, *fastest;
 115
 116         fastest = XOR_SELECT_TEMPLATE(NULL);
 117
 118         if (fastest) {
 119                 printk(KERN_INFO "xor: automatically using best "
 120                                  "checksumming function   %-10s\n",
 121                        fastest->name);
 122                 goto out;
 123         }
 124
 125         /*
 126          * Note: Since the memory is not actually used for _anything_ but to
 127          * test the XOR speed, we don't really want kmemcheck to warn about
 128          * reading uninitialized bytes here.
 129          */
 130         b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 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 through
 139          * all the possible functions, just test the best one
 140          */
 141
 142 #define xor_speed(templ)        do_xor_speed((templ), b1, b2)
 143
 144         printk(KERN_INFO "xor: measuring software checksum speed\n");
 145         XOR_TRY_TEMPLATES;
 146         fastest = template_list;
 147         for (f = fastest; f; f = f->next)
 148                 if (f->speed > fastest->speed)
 149                         fastest = f;
 150
 151         printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
 152                fastest->name, fastest->speed / 1000, fastest->speed % 1000);
 153
 154 #undef xor_speed
 155
 156         free_pages((unsigned long)b1, 2);
 157 out:
 158         active_template = fastest;
 159         return 0;
 160 }
 161
 162 static __exit void xor_exit(void) { }
 163
 164 MODULE_LICENSE("GPL");
 165
 166 /* when built-in xor.o must initialize before drivers/md/md.o */
 167 core_initcall(calibrate_xor_blocks);
 168 module_exit(xor_exit);