lib/raid6/algos.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  * raid6/algos.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 #include <linux/gfp.h>
  25 #if !RAID6_USE_EMPTY_ZERO_PAGE
  26 /* In .bss so it's zeroed */
  27 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
  28 EXPORT_SYMBOL(raid6_empty_zero_page);
  29 #endif
  30 #endif
  31
  32 struct raid6_calls raid6_call;
  33 EXPORT_SYMBOL_GPL(raid6_call);
  34
  35 const struct raid6_calls * const raid6_algos[] = {
  36         &raid6_intx1,
  37         &raid6_intx2,
  38         &raid6_intx4,
  39         &raid6_intx8,
  40 #if defined(__ia64__)
  41         &raid6_intx16,
  42         &raid6_intx32,
  43 #endif
  44 #if defined(__i386__) && !defined(__arch_um__)
  45         &raid6_mmxx1,
  46         &raid6_mmxx2,
  47         &raid6_sse1x1,
  48         &raid6_sse1x2,
  49         &raid6_sse2x1,
  50         &raid6_sse2x2,
  51 #endif
  52 #if defined(__x86_64__) && !defined(__arch_um__)
  53         &raid6_sse2x1,
  54         &raid6_sse2x2,
  55         &raid6_sse2x4,
  56 #endif
  57 #ifdef CONFIG_ALTIVEC
  58         &raid6_altivec1,
  59         &raid6_altivec2,
  60         &raid6_altivec4,
  61         &raid6_altivec8,
  62 #endif
  63         NULL
  64 };
  65
  66 #ifdef __KERNEL__
  67 #define RAID6_TIME_JIFFIES_LG2  4
  68 #else
  69 /* Need more time to be stable in userspace */
  70 #define RAID6_TIME_JIFFIES_LG2  9
  71 #define time_before(x, y) ((x) < (y))
  72 #endif
  73
  74 /* Try to pick the best algorithm */
  75 /* This code uses the gfmul table as convenient data set to abuse */
  76
  77 int __init raid6_select_algo(void)
  78 {
  79         const struct raid6_calls * const * algo;
  80         const struct raid6_calls * best;
  81         char *syndromes;
  82         void *dptrs[(65536/PAGE_SIZE)+2];
  83         int i, disks;
  84         unsigned long perf, bestperf;
  85         int bestprefer;
  86         unsigned long j0, j1;
  87
  88         disks = (65536/PAGE_SIZE)+2;
  89         for ( i = 0 ; i < disks-2 ; i++ ) {
  90                 dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
  91         }
  92
  93         /* Normal code - use a 2-page allocation to avoid D$ conflict */
  94         syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
  95
  96         if ( !syndromes ) {
  97                 printk("raid6: Yikes!  No memory available.\n");
  98                 return -ENOMEM;
  99         }
 100
 101         dptrs[disks-2] = syndromes;
 102         dptrs[disks-1] = syndromes + PAGE_SIZE;
 103
 104         bestperf = 0;  bestprefer = 0;  best = NULL;
 105
 106         for ( algo = raid6_algos ; *algo ; algo++ ) {
 107                 if ( !(*algo)->valid || (*algo)->valid() ) {
 108                         perf = 0;
 109
 110                         preempt_disable();
 111                         j0 = jiffies;
 112                         while ( (j1 = jiffies) == j0 )
 113                                 cpu_relax();
 114                         while (time_before(jiffies,
 115                                             j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
 116                                 (*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
 117                                 perf++;
 118                         }
 119                         preempt_enable();
 120
 121                         if ( (*algo)->prefer > bestprefer ||
 122                              ((*algo)->prefer == bestprefer &&
 123                               perf > bestperf) ) {
 124                                 best = *algo;
 125                                 bestprefer = best->prefer;
 126                                 bestperf = perf;
 127                         }
 128                         printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
 129                                (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
 130                 }
 131         }
 132
 133         if (best) {
 134                 printk("raid6: using algorithm %s (%ld MB/s)\n",
 135                        best->name,
 136                        (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
 137                 raid6_call = *best;
 138         } else
 139                 printk("raid6: Yikes!  No algorithm found!\n");
 140
 141         free_pages((unsigned long)syndromes, 1);
 142
 143         return best ? 0 : -EINVAL;
 144 }
 145
 146 static void raid6_exit(void)
 147 {
 148         do { } while (0);
 149 }
 150
 151 subsys_initcall(raid6_select_algo);
 152 module_exit(raid6_exit);
 153 MODULE_LICENSE("GPL");
 154 MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");