aboutsummaryrefslogtreecommitdiffstats
path: root/lib/raid6/algos.c
blob: b595f560bee74ba855da88bbc1793bf7eb193312 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright 2002 H. Peter Anvin - All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
 *   Boston MA 02111-1307, USA; either version 2 of the License, or
 *   (at your option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * raid6/algos.c
 *
 * Algorithm list and algorithm selection for RAID-6
 */

#include <linux/raid/pq.h>
#ifndef __KERNEL__
#include <sys/mman.h>
#include <stdio.h>
#else
#include <linux/gfp.h>
#if !RAID6_USE_EMPTY_ZERO_PAGE
/* In .bss so it's zeroed */
const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
EXPORT_SYMBOL(raid6_empty_zero_page);
#endif
#endif

struct raid6_calls raid6_call;
EXPORT_SYMBOL_GPL(raid6_call);

const struct raid6_calls * const raid6_algos[] = {
	&raid6_intx1,
	&raid6_intx2,
	&raid6_intx4,
	&raid6_intx8,
#if defined(__ia64__)
	&raid6_intx16,
	&raid6_intx32,
#endif
#if defined(__i386__) && !defined(__arch_um__)
	&raid6_mmxx1,
	&raid6_mmxx2,
	&raid6_sse1x1,
	&raid6_sse1x2,
	&raid6_sse2x1,
	&raid6_sse2x2,
#endif
#if defined(__x86_64__) && !defined(__arch_um__)
	&raid6_sse2x1,
	&raid6_sse2x2,
	&raid6_sse2x4,
#endif
#ifdef CONFIG_ALTIVEC
	&raid6_altivec1,
	&raid6_altivec2,
	&raid6_altivec4,
	&raid6_altivec8,
#endif
	NULL
};

#ifdef __KERNEL__
#define RAID6_TIME_JIFFIES_LG2	4
#else
/* Need more time to be stable in userspace */
#define RAID6_TIME_JIFFIES_LG2	9
#define time_before(x, y) ((x) < (y))
#endif

/* Try to pick the best algorithm */
/* This code uses the gfmul table as convenient data set to abuse */

int __init raid6_select_algo(void)
{
	const struct raid6_calls * const * algo;
	const struct raid6_calls * best;
	char *syndromes;
	void *dptrs[(65536/PAGE_SIZE)+2];
	int i, disks;
	unsigned long perf, bestperf;
	int bestprefer;
	unsigned long j0, j1;

	disks = (65536/PAGE_SIZE)+2;
	for ( i = 0 ; i < disks-2 ; i++ ) {
		dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
	}

	/* Normal code - use a 2-page allocation to avoid D$ conflict */
	syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);

	if ( !syndromes ) {
		printk("raid6: Yikes!  No memory available.\n");
		return -ENOMEM;
	}

	dptrs[disks-2] = syndromes;
	dptrs[disks-1] = syndromes + PAGE_SIZE;

	bestperf = 0;  bestprefer = 0;  best = NULL;

	for ( algo = raid6_algos ; *algo ; algo++ ) {
		if ( !(*algo)->valid || (*algo)->valid() ) {
			perf = 0;

			preempt_disable();
			j0 = jiffies;
			while ( (j1 = jiffies) == j0 )
				cpu_relax();
			while (time_before(jiffies,
					    j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
				(*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
				perf++;
			}
			preempt_enable();

			if ( (*algo)->prefer > bestprefer ||
			     ((*algo)->prefer == bestprefer &&
			      perf > bestperf) ) {
				best = *algo;
				bestprefer = best->prefer;
				bestperf = perf;
			}
			printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
			       (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
		}
	}

	if (best) {
		printk("raid6: using algorithm %s (%ld MB/s)\n",
		       best->name,
		       (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
		raid6_call = *best;
	} else
		printk("raid6: Yikes!  No algorithm found!\n");

	free_pages((unsigned long)syndromes, 1);

	return best ? 0 : -EINVAL;
}

static void raid6_exit(void)
{
	do { } while (0);
}

subsys_initcall(raid6_select_algo);
module_exit(raid6_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");

Privacy Policy