drivers/md/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/raid/md.h>
  22 #include <linux/raid/xor.h>
  23 #include <asm/xor.h>
  24
  25 /* The xor routines to use.  */
  26 static struct xor_block_template *active_template;
  27
  28 void
  29 xor_block(unsigned int count, unsigned int bytes, void **ptr)
  30 {
  31         unsigned long *p0, *p1, *p2, *p3, *p4;
  32
  33         p0 = (unsigned long *) ptr[0];
  34         p1 = (unsigned long *) ptr[1];
  35         if (count == 2) {
  36                 active_template->do_2(bytes, p0, p1);
  37                 return;
  38         }
  39
  40         p2 = (unsigned long *) ptr[2];
  41         if (count == 3) {
  42                 active_template->do_3(bytes, p0, p1, p2);
  43                 return;
  44         }
  45
  46         p3 = (unsigned long *) ptr[3];
  47         if (count == 4) {
  48                 active_template->do_4(bytes, p0, p1, p2, p3);
  49                 return;
  50         }
  51
  52         p4 = (unsigned long *) ptr[4];
  53         active_template->do_5(bytes, p0, p1, p2, p3, p4);
  54 }
  55
  56 /* Set of all registered templates.  */
  57 static struct xor_block_template *template_list;
  58
  59 #define BENCH_SIZE (PAGE_SIZE)
  60
  61 static void
  62 do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
  63 {
  64         int speed;
  65         unsigned long now;
  66         int i, count, max;
  67
  68         tmpl->next = template_list;
  69         template_list = tmpl;
  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                 now = jiffies;
  79                 count = 0;
  80                 while (jiffies == now) {
  81                         mb();
  82                         tmpl->do_2(BENCH_SIZE, b1, b2);
  83                         mb();
  84                         count++;
  85                         mb();
  86                 }
  87                 if (count > max)
  88                         max = count;
  89         }
  90
  91         speed = max * (HZ * BENCH_SIZE / 1024);
  92         tmpl->speed = speed;
  93
  94         printk("   %-10s: %5d.%03d MB/sec\n", tmpl->name,
  95                speed / 1000, speed % 1000);
  96 }
  97
  98 static int
  99 calibrate_xor_block(void)
 100 {
 101         void *b1, *b2;
 102         struct xor_block_template *f, *fastest;
 103
 104         b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
 105         if (! b1) {
 106                 printk("raid5: Yikes!  No memory available.\n");
 107                 return -ENOMEM;
 108         }
 109         b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
 110
 111         /*
 112          * If this arch/cpu has a short-circuited selection, don't loop through all
 113          * the possible functions, just test the best one
 114          */
 115
 116         fastest = NULL;
 117
 118 #ifdef XOR_SELECT_TEMPLATE
 119                 fastest = XOR_SELECT_TEMPLATE(fastest);
 120 #endif
 121
 122 #define xor_speed(templ)        do_xor_speed((templ), b1, b2)
 123
 124         if (fastest) {
 125                 printk(KERN_INFO "raid5: automatically using best checksumming function: %s\n",
 126                         fastest->name);
 127                 xor_speed(fastest);
 128         } else {
 129                 printk(KERN_INFO "raid5: measuring checksumming speed\n");
 130                 XOR_TRY_TEMPLATES;
 131                 fastest = template_list;
 132                 for (f = fastest; f; f = f->next)
 133                         if (f->speed > fastest->speed)
 134                                 fastest = f;
 135         }
 136
 137         printk("raid5: using function: %s (%d.%03d MB/sec)\n",
 138                fastest->name, fastest->speed / 1000, fastest->speed % 1000);
 139
 140 #undef xor_speed
 141
 142         free_pages((unsigned long)b1, 2);
 143
 144         active_template = fastest;
 145         return 0;
 146 }
 147
 148 static __exit void xor_exit(void) { }
 149
 150 EXPORT_SYMBOL(xor_block);
 151 MODULE_LICENSE("GPL");
 152
 153 module_init(calibrate_xor_block);
 154 module_exit(xor_exit);