1 /* -*- linux-c -*- ------------------------------------------------------- *
3 * Copyright 2002 H. Peter Anvin - All Rights Reserved
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.
11 * ----------------------------------------------------------------------- */
16 * Algorithm list and algorithm selection for RAID-6
19 #include <linux/raid/pq.h>
24 #if !RAID6_USE_EMPTY_ZERO_PAGE
25 /* In .bss so it's zeroed */
26 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
27 EXPORT_SYMBOL(raid6_empty_zero_page);
31 struct raid6_calls raid6_call;
32 EXPORT_SYMBOL_GPL(raid6_call);
34 const struct raid6_calls * const raid6_algos[] = {
43 #if defined(__i386__) && !defined(__arch_um__)
51 #if defined(__x86_64__) && !defined(__arch_um__)
66 #define RAID6_TIME_JIFFIES_LG2 4
68 /* Need more time to be stable in userspace */
69 #define RAID6_TIME_JIFFIES_LG2 9
70 #define time_before(x, y) ((x) < (y))
73 /* Try to pick the best algorithm */
74 /* This code uses the gfmul table as convenient data set to abuse */
76 int __init raid6_select_algo(void)
78 const struct raid6_calls * const * algo;
79 const struct raid6_calls * best;
81 void *dptrs[(65536/PAGE_SIZE)+2];
83 unsigned long perf, bestperf;
87 disks = (65536/PAGE_SIZE)+2;
88 for ( i = 0 ; i < disks-2 ; i++ ) {
89 dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
92 /* Normal code - use a 2-page allocation to avoid D$ conflict */
93 syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
96 printk("raid6: Yikes! No memory available.\n");
100 dptrs[disks-2] = syndromes;
101 dptrs[disks-1] = syndromes + PAGE_SIZE;
103 bestperf = 0; bestprefer = 0; best = NULL;
105 for ( algo = raid6_algos ; *algo ; algo++ ) {
106 if ( !(*algo)->valid || (*algo)->valid() ) {
111 while ( (j1 = jiffies) == j0 )
113 while (time_before(jiffies,
114 j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
115 (*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
120 if ( (*algo)->prefer > bestprefer ||
121 ((*algo)->prefer == bestprefer &&
124 bestprefer = best->prefer;
127 printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
128 (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
133 printk("raid6: using algorithm %s (%ld MB/s)\n",
135 (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
138 printk("raid6: Yikes! No algorithm found!\n");
140 free_pages((unsigned long)syndromes, 1);
142 return best ? 0 : -EINVAL;
145 static void raid6_exit(void)
150 subsys_initcall(raid6_select_algo);
151 module_exit(raid6_exit);
152 MODULE_LICENSE("GPL");
153 MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");