projects/linux·blob v3.2 · refs

155 lines · 3.7 KiB

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#include <linux/module.h>
21#ifndef __KERNEL__
22#include <sys/mman.h>
23#include <stdio.h>
24#else
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 &raid6_intx1,
38 &raid6_intx2,
39 &raid6_intx4,
40 &raid6_intx8,
41#if defined(__ia64__)
42 &raid6_intx16,
43 &raid6_intx32,
44#endif
45#if defined(__i386__) && !defined(__arch_um__)
46 &raid6_mmxx1,
47 &raid6_mmxx2,
48 &raid6_sse1x1,
49 &raid6_sse1x2,
50 &raid6_sse2x1,
51 &raid6_sse2x2,
52#endif
53#if defined(__x86_64__) && !defined(__arch_um__)
54 &raid6_sse2x1,
55 &raid6_sse2x2,
56 &raid6_sse2x4,
57#endif
58#ifdef CONFIG_ALTIVEC
59 &raid6_altivec1,
60 &raid6_altivec2,
61 &raid6_altivec4,
62 &raid6_altivec8,
63#endif
64 NULL
65};
66
67#ifdef __KERNEL__
68#define RAID6_TIME_JIFFIES_LG2 4
69#else
70/* Need more time to be stable in userspace */
71#define RAID6_TIME_JIFFIES_LG2 9
72#define time_before(x, y) ((x) < (y))
73#endif
74
75/* Try to pick the best algorithm */
76/* This code uses the gfmul table as convenient data set to abuse */
77
78int __init raid6_select_algo(void)
79{
80 const struct raid6_calls * const * algo;
81 const struct raid6_calls * best;
82 char *syndromes;
83 void *dptrs[(65536/PAGE_SIZE)+2];
84 int i, disks;
85 unsigned long perf, bestperf;
86 int bestprefer;
87 unsigned long j0, j1;
88
89 disks = (65536/PAGE_SIZE)+2;
90 for ( i = 0 ; i < disks-2 ; i++ ) {
91 dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
92 }
93
94 /* Normal code - use a 2-page allocation to avoid D$ conflict */
95 syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
96
97 if ( !syndromes ) {
98 printk("raid6: Yikes! No memory available.\n");
99 return -ENOMEM;
100 }
101
102 dptrs[disks-2] = syndromes;
103 dptrs[disks-1] = syndromes + PAGE_SIZE;
104
105 bestperf = 0; bestprefer = 0; best = NULL;
106
107 for ( algo = raid6_algos ; *algo ; algo++ ) {
108 if ( !(*algo)->valid || (*algo)->valid() ) {
109 perf = 0;
110
111 preempt_disable();
112 j0 = jiffies;
113 while ( (j1 = jiffies) == j0 )
114 cpu_relax();
115 while (time_before(jiffies,
116 j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
117 (*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
118 perf++;
119 }
120 preempt_enable();
121
122 if ( (*algo)->prefer > bestprefer ||
123 ((*algo)->prefer == bestprefer &&
124 perf > bestperf) ) {
125 best = *algo;
126 bestprefer = best->prefer;
127 bestperf = perf;
128 }
129 printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
130 (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
131 }
132 }
133
134 if (best) {
135 printk("raid6: using algorithm %s (%ld MB/s)\n",
136 best->name,
137 (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
138 raid6_call = *best;
139 } else
140 printk("raid6: Yikes! No algorithm found!\n");
141
142 free_pages((unsigned long)syndromes, 1);
143
144 return best ? 0 : -EINVAL;
145}
146
147static void raid6_exit(void)
148{
149 do { } while (0);
150}
151
152subsys_initcall(raid6_select_algo);
153module_exit(raid6_exit);
154MODULE_LICENSE("GPL");
155MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");