xref: /linux/lib/raid6/algos.c (revision d39d0ed196aa1685bb24771e92f78633c66ac9cb)
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/gfp.h>
25 #if !RAID6_USE_EMPTY_ZERO_PAGE
26 /* In .bss so it's zeroed */
27 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
28 EXPORT_SYMBOL(raid6_empty_zero_page);
29 #endif
30 #endif
31 
32 struct raid6_calls raid6_call;
33 EXPORT_SYMBOL_GPL(raid6_call);
34 
35 const struct raid6_calls * const raid6_algos[] = {
36 	&raid6_intx1,
37 	&raid6_intx2,
38 	&raid6_intx4,
39 	&raid6_intx8,
40 #if defined(__ia64__)
41 	&raid6_intx16,
42 	&raid6_intx32,
43 #endif
44 #if defined(__i386__) && !defined(__arch_um__)
45 	&raid6_mmxx1,
46 	&raid6_mmxx2,
47 	&raid6_sse1x1,
48 	&raid6_sse1x2,
49 	&raid6_sse2x1,
50 	&raid6_sse2x2,
51 #endif
52 #if defined(__x86_64__) && !defined(__arch_um__)
53 	&raid6_sse2x1,
54 	&raid6_sse2x2,
55 	&raid6_sse2x4,
56 #endif
57 #ifdef CONFIG_ALTIVEC
58 	&raid6_altivec1,
59 	&raid6_altivec2,
60 	&raid6_altivec4,
61 	&raid6_altivec8,
62 #endif
63 	NULL
64 };
65 
66 #ifdef __KERNEL__
67 #define RAID6_TIME_JIFFIES_LG2	4
68 #else
69 /* Need more time to be stable in userspace */
70 #define RAID6_TIME_JIFFIES_LG2	9
71 #define time_before(x, y) ((x) < (y))
72 #endif
73 
74 /* Try to pick the best algorithm */
75 /* This code uses the gfmul table as convenient data set to abuse */
76 
77 int __init raid6_select_algo(void)
78 {
79 	const struct raid6_calls * const * algo;
80 	const struct raid6_calls * best;
81 	char *syndromes;
82 	void *dptrs[(65536/PAGE_SIZE)+2];
83 	int i, disks;
84 	unsigned long perf, bestperf;
85 	int bestprefer;
86 	unsigned long j0, j1;
87 
88 	disks = (65536/PAGE_SIZE)+2;
89 	for ( i = 0 ; i < disks-2 ; i++ ) {
90 		dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
91 	}
92 
93 	/* Normal code - use a 2-page allocation to avoid D$ conflict */
94 	syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
95 
96 	if ( !syndromes ) {
97 		printk("raid6: Yikes!  No memory available.\n");
98 		return -ENOMEM;
99 	}
100 
101 	dptrs[disks-2] = syndromes;
102 	dptrs[disks-1] = syndromes + PAGE_SIZE;
103 
104 	bestperf = 0;  bestprefer = 0;  best = NULL;
105 
106 	for ( algo = raid6_algos ; *algo ; algo++ ) {
107 		if ( !(*algo)->valid || (*algo)->valid() ) {
108 			perf = 0;
109 
110 			preempt_disable();
111 			j0 = jiffies;
112 			while ( (j1 = jiffies) == j0 )
113 				cpu_relax();
114 			while (time_before(jiffies,
115 					    j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
116 				(*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
117 				perf++;
118 			}
119 			preempt_enable();
120 
121 			if ( (*algo)->prefer > bestprefer ||
122 			     ((*algo)->prefer == bestprefer &&
123 			      perf > bestperf) ) {
124 				best = *algo;
125 				bestprefer = best->prefer;
126 				bestperf = perf;
127 			}
128 			printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
129 			       (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
130 		}
131 	}
132 
133 	if (best) {
134 		printk("raid6: using algorithm %s (%ld MB/s)\n",
135 		       best->name,
136 		       (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
137 		raid6_call = *best;
138 	} else
139 		printk("raid6: Yikes!  No algorithm found!\n");
140 
141 	free_pages((unsigned long)syndromes, 1);
142 
143 	return best ? 0 : -EINVAL;
144 }
145 
146 static void raid6_exit(void)
147 {
148 	do { } while (0);
149 }
150 
151 subsys_initcall(raid6_select_algo);
152 module_exit(raid6_exit);
153 MODULE_LICENSE("GPL");
154 MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");
155