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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 */
29 EXPORT_SYMBOL(raid6_empty_zero_page);
30 #endif
31 #endif
32 
35 
36 const 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
59 #endif
60  &raid6_intx1,
61  &raid6_intx2,
62  &raid6_intx4,
63  &raid6_intx8,
64  NULL
65 };
66 
69 
72 
73 const struct raid6_recov_calls *const raid6_recov_algos[] = {
74 #if (defined(__i386__) || defined(__x86_64__)) && !defined(__arch_um__)
76 #endif
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 
89 static 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 
110 static 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 
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 
194 static void raid6_exit(void)
195 {
196  do { } while (0);
197 }
198 
200 module_exit(raid6_exit);
201 MODULE_LICENSE("GPL");
202 MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");