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