LXR linux/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 */
  26const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
  27EXPORT_SYMBOL(raid6_empty_zero_page);
  28#endif
  29#endif
  30
  31struct raid6_calls raid6_call;
  32EXPORT_SYMBOL_GPL(raid6_call);
  33
  34/* Various routine sets */
  35extern const struct raid6_calls raid6_intx1;
  36extern const struct raid6_calls raid6_intx2;
  37extern const struct raid6_calls raid6_intx4;
  38extern const struct raid6_calls raid6_intx8;
  39extern const struct raid6_calls raid6_intx16;
  40extern const struct raid6_calls raid6_intx32;
  41extern const struct raid6_calls raid6_mmxx1;
  42extern const struct raid6_calls raid6_mmxx2;
  43extern const struct raid6_calls raid6_sse1x1;
  44extern const struct raid6_calls raid6_sse1x2;
  45extern const struct raid6_calls raid6_sse2x1;
  46extern const struct raid6_calls raid6_sse2x2;
  47extern const struct raid6_calls raid6_sse2x4;
  48extern const struct raid6_calls raid6_altivec1;
  49extern const struct raid6_calls raid6_altivec2;
  50extern const struct raid6_calls raid6_altivec4;
  51extern const struct raid6_calls raid6_altivec8;
  52
  53const 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
  95int __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
 164static void raid6_exit(void)
 165{
 166        do { } while (0);
 167}
 168
 169subsys_initcall(raid6_select_algo);
 170module_exit(raid6_exit);
 171MODULE_LICENSE("GPL");
 172