drivers/md/raid6algos.c

   1 /* -*- linux-c -*- ------------------------------------------------------- *
   2  *
   3  *   Copyright 2002 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
   8  *   Boston MA 02111-1307, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * raid6algos.c
  15  *
  16  * Algorithm list and algorithm selection for RAID-6
  17  */
  18
  19 #include <linux/raid/pq.h>
  20 #ifndef __KERNEL__
  21 #include <sys/mman.h>
  22 #include <stdio.h>
  23 #else
  24 #if !RAID6_USE_EMPTY_ZERO_PAGE
  25 /* In .bss so it's zeroed */
  26 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
  27 EXPORT_SYMBOL(raid6_empty_zero_page);
  28 #endif
  29 #endif
  30
  31 struct raid6_calls raid6_call;
  32 EXPORT_SYMBOL_GPL(raid6_call);
  33
  34 /* Various routine sets */
  35 extern const struct raid6_calls raid6_intx1;
  36 extern const struct raid6_calls raid6_intx2;
  37 extern const struct raid6_calls raid6_intx4;
  38 extern const struct raid6_calls raid6_intx8;
  39 extern const struct raid6_calls raid6_intx16;
  40 extern const struct raid6_calls raid6_intx32;
  41 extern const struct raid6_calls raid6_mmxx1;
  42 extern const struct raid6_calls raid6_mmxx2;
  43 extern const struct raid6_calls raid6_sse1x1;
  44 extern const struct raid6_calls raid6_sse1x2;
  45 extern const struct raid6_calls raid6_sse2x1;
  46 extern const struct raid6_calls raid6_sse2x2;
  47 extern const struct raid6_calls raid6_sse2x4;
  48 extern const struct raid6_calls raid6_altivec1;
  49 extern const struct raid6_calls raid6_altivec2;
  50 extern const struct raid6_calls raid6_altivec4;
  51 extern const struct raid6_calls raid6_altivec8;
  52
  53 const struct raid6_calls * const raid6_algos[] = {
  54         &raid6_intx1,
  55         &raid6_intx2,
  56         &raid6_intx4,
  57         &raid6_intx8,
  58 #if defined(__ia64__)
  59         &raid6_intx16,
  60         &raid6_intx32,
  61 #endif
  62 #if defined(__i386__) && !defined(__arch_um__)
  63         &raid6_mmxx1,
  64         &raid6_mmxx2,
  65         &raid6_sse1x1,
  66         &raid6_sse1x2,
  67         &raid6_sse2x1,
  68         &raid6_sse2x2,
  69 #endif
  70 #if defined(__x86_64__) && !defined(__arch_um__)
  71         &raid6_sse2x1,
  72         &raid6_sse2x2,
  73         &raid6_sse2x4,
  74 #endif
  75 #ifdef CONFIG_ALTIVEC
  76         &raid6_altivec1,
  77         &raid6_altivec2,
  78         &raid6_altivec4,
  79         &raid6_altivec8,
  80 #endif
  81         NULL
  82 };
  83
  84 #ifdef __KERNEL__
  85 #define RAID6_TIME_JIFFIES_LG2  4
  86 #else
  87 /* Need more time to be stable in userspace */
  88 #define RAID6_TIME_JIFFIES_LG2  9
  89 #define time_before(x, y) ((x) < (y))
  90 #endif
  91
  92 /* Try to pick the best algorithm */
  93 /* This code uses the gfmul table as convenient data set to abuse */
  94
  95 int __init raid6_select_algo(void)
  96 {
  97         const struct raid6_calls * const * algo;
  98         const struct raid6_calls * best;
  99         char *syndromes;
 100         void *dptrs[(65536/PAGE_SIZE)+2];
 101         int i, disks;
 102         unsigned long perf, bestperf;
 103         int bestprefer;
 104         unsigned long j0, j1;
 105
 106         disks = (65536/PAGE_SIZE)+2;
 107         for ( i = 0 ; i < disks-2 ; i++ ) {
 108                 dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
 109         }
 110
 111         /* Normal code - use a 2-page allocation to avoid D$ conflict */
 112         syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
 113
 114         if ( !syndromes ) {
 115                 printk("raid6: Yikes!  No memory available.\n");
 116                 return -ENOMEM;
 117         }
 118
 119         dptrs[disks-2] = syndromes;
 120         dptrs[disks-1] = syndromes + PAGE_SIZE;
 121
 122         bestperf = 0;  bestprefer = 0;  best = NULL;
 123
 124         for ( algo = raid6_algos ; *algo ; algo++ ) {
 125                 if ( !(*algo)->valid || (*algo)->valid() ) {
 126                         perf = 0;
 127
 128                         preempt_disable();
 129                         j0 = jiffies;
 130                         while ( (j1 = jiffies) == j0 )
 131                                 cpu_relax();
 132                         while (time_before(jiffies,
 133                                             j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
 134                                 (*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
 135                                 perf++;
 136                         }
 137                         preempt_enable();
 138
 139                         if ( (*algo)->prefer > bestprefer ||
 140                              ((*algo)->prefer == bestprefer &&
 141                               perf > bestperf) ) {
 142                                 best = *algo;
 143                                 bestprefer = best->prefer;
 144                                 bestperf = perf;
 145                         }
 146                         printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
 147                                (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
 148                 }
 149         }
 150
 151         if (best) {
 152                 printk("raid6: using algorithm %s (%ld MB/s)\n",
 153                        best->name,
 154                        (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
 155                 raid6_call = *best;
 156         } else
 157                 printk("raid6: Yikes!  No algorithm found!\n");
 158
 159         free_pages((unsigned long)syndromes, 1);
 160
 161         return best ? 0 : -EINVAL;
 162 }
 163
 164 static void raid6_exit(void)
 165 {
 166         do { } while (0);
 167 }
 168
 169 subsys_initcall(raid6_select_algo);
 170 module_exit(raid6_exit);
 171 MODULE_LICENSE("GPL");