linux/lib/raid6/algos.c
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   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/module.h>
  25#include <linux/gfp.h>
  26#if !RAID6_USE_EMPTY_ZERO_PAGE
  27/* In .bss so it's zeroed */
  28const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
  29EXPORT_SYMBOL(raid6_empty_zero_page);
  30#endif
  31#endif
  32
  33struct raid6_calls raid6_call;
  34EXPORT_SYMBOL_GPL(raid6_call);
  35
  36const struct raid6_calls * const raid6_algos[] = {
  37#if defined(__ia64__)
  38        &raid6_intx16,
  39        &raid6_intx32,
  40#endif
  41#if defined(__i386__) && !defined(__arch_um__)
  42        &raid6_mmxx1,
  43        &raid6_mmxx2,
  44        &raid6_sse1x1,
  45        &raid6_sse1x2,
  46        &raid6_sse2x1,
  47        &raid6_sse2x2,
  48#endif
  49#if defined(__x86_64__) && !defined(__arch_um__)
  50        &raid6_sse2x1,
  51        &raid6_sse2x2,
  52        &raid6_sse2x4,
  53#endif
  54#ifdef CONFIG_ALTIVEC
  55        &raid6_altivec1,
  56        &raid6_altivec2,
  57        &raid6_altivec4,
  58        &raid6_altivec8,
  59#endif
  60        &raid6_intx1,
  61        &raid6_intx2,
  62        &raid6_intx4,
  63        &raid6_intx8,
  64        NULL
  65};
  66
  67void (*raid6_2data_recov)(int, size_t, int, int, void **);
  68EXPORT_SYMBOL_GPL(raid6_2data_recov);
  69
  70void (*raid6_datap_recov)(int, size_t, int, void **);
  71EXPORT_SYMBOL_GPL(raid6_datap_recov);
  72
  73const struct raid6_recov_calls *const raid6_recov_algos[] = {
  74#if (defined(__i386__) || defined(__x86_64__)) && !defined(__arch_um__)
  75        &raid6_recov_ssse3,
  76#endif
  77        &raid6_recov_intx1,
  78        NULL
  79};
  80
  81#ifdef __KERNEL__
  82#define RAID6_TIME_JIFFIES_LG2  4
  83#else
  84/* Need more time to be stable in userspace */
  85#define RAID6_TIME_JIFFIES_LG2  9
  86#define time_before(x, y) ((x) < (y))
  87#endif
  88
  89static inline const struct raid6_recov_calls *raid6_choose_recov(void)
  90{
  91        const struct raid6_recov_calls *const *algo;
  92        const struct raid6_recov_calls *best;
  93
  94        for (best = NULL, algo = raid6_recov_algos; *algo; algo++)
  95                if (!best || (*algo)->priority > best->priority)
  96                        if (!(*algo)->valid || (*algo)->valid())
  97                                best = *algo;
  98
  99        if (best) {
 100                raid6_2data_recov = best->data2;
 101                raid6_datap_recov = best->datap;
 102
 103                printk("raid6: using %s recovery algorithm\n", best->name);
 104        } else
 105                printk("raid6: Yikes! No recovery algorithm found!\n");
 106
 107        return best;
 108}
 109
 110static inline const struct raid6_calls *raid6_choose_gen(
 111        void *(*const dptrs)[(65536/PAGE_SIZE)+2], const int disks)
 112{
 113        unsigned long perf, bestperf, j0, j1;
 114        const struct raid6_calls *const *algo;
 115        const struct raid6_calls *best;
 116
 117        for (bestperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
 118                if (!best || (*algo)->prefer >= best->prefer) {
 119                        if ((*algo)->valid && !(*algo)->valid())
 120                                continue;
 121
 122                        perf = 0;
 123
 124                        preempt_disable();
 125                        j0 = jiffies;
 126                        while ((j1 = jiffies) == j0)
 127                                cpu_relax();
 128                        while (time_before(jiffies,
 129                                            j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
 130                                (*algo)->gen_syndrome(disks, PAGE_SIZE, *dptrs);
 131                                perf++;
 132                        }
 133                        preempt_enable();
 134
 135                        if (perf > bestperf) {
 136                                bestperf = perf;
 137                                best = *algo;
 138                        }
 139                        printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
 140                               (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
 141                }
 142        }
 143
 144        if (best) {
 145                printk("raid6: using algorithm %s (%ld MB/s)\n",
 146                       best->name,
 147                       (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
 148                raid6_call = *best;
 149        } else
 150                printk("raid6: Yikes!  No algorithm found!\n");
 151
 152        return best;
 153}
 154
 155
 156/* Try to pick the best algorithm */
 157/* This code uses the gfmul table as convenient data set to abuse */
 158
 159int __init raid6_select_algo(void)
 160{
 161        const int disks = (65536/PAGE_SIZE)+2;
 162
 163        const struct raid6_calls *gen_best;
 164        const struct raid6_recov_calls *rec_best;
 165        char *syndromes;
 166        void *dptrs[(65536/PAGE_SIZE)+2];
 167        int i;
 168
 169        for (i = 0; i < disks-2; i++)
 170                dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
 171
 172        /* Normal code - use a 2-page allocation to avoid D$ conflict */
 173        syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
 174
 175        if (!syndromes) {
 176                printk("raid6: Yikes!  No memory available.\n");
 177                return -ENOMEM;
 178        }
 179
 180        dptrs[disks-2] = syndromes;
 181        dptrs[disks-1] = syndromes + PAGE_SIZE;
 182
 183        /* select raid gen_syndrome function */
 184        gen_best = raid6_choose_gen(&dptrs, disks);
 185
 186        /* select raid recover functions */
 187        rec_best = raid6_choose_recov();
 188
 189        free_pages((unsigned long)syndromes, 1);
 190
 191        return gen_best && rec_best ? 0 : -EINVAL;
 192}
 193
 194static void raid6_exit(void)
 195{
 196        do { } while (0);
 197}
 198
 199subsys_initcall(raid6_select_algo);
 200module_exit(raid6_exit);
 201MODULE_LICENSE("GPL");
 202MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");
 203
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