tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
34const 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
76int __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
145static void raid6_exit(void)
146{
147 do { } while (0);
148}
149
150subsys_initcall(raid6_select_algo);
151module_exit(raid6_exit);
152MODULE_LICENSE("GPL");
153MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");