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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>
20 #include <linux/module.h>
25 #include <linux/gfp.h>
26 #if !RAID6_USE_EMPTY_ZERO_PAGE
27 /* In .bss so it's zeroed */
28 const char raid6_empty_zero_page
[PAGE_SIZE
] __attribute__((aligned(256)));
29 EXPORT_SYMBOL(raid6_empty_zero_page
);
33 struct raid6_calls raid6_call
;
34 EXPORT_SYMBOL_GPL(raid6_call
);
36 const struct raid6_calls
* const raid6_algos
[] = {
45 #if defined(__i386__) && !defined(__arch_um__)
53 #if defined(__x86_64__) && !defined(__arch_um__)
68 #define RAID6_TIME_JIFFIES_LG2 4
70 /* Need more time to be stable in userspace */
71 #define RAID6_TIME_JIFFIES_LG2 9
72 #define time_before(x, y) ((x) < (y))
75 /* Try to pick the best algorithm */
76 /* This code uses the gfmul table as convenient data set to abuse */
78 int __init
raid6_select_algo(void)
80 const struct raid6_calls
* const * algo
;
81 const struct raid6_calls
* best
;
83 void *dptrs
[(65536/PAGE_SIZE
)+2];
85 unsigned long perf
, bestperf
;
89 disks
= (65536/PAGE_SIZE
)+2;
90 for ( i
= 0 ; i
< disks
-2 ; i
++ ) {
91 dptrs
[i
] = ((char *)raid6_gfmul
) + PAGE_SIZE
*i
;
94 /* Normal code - use a 2-page allocation to avoid D$ conflict */
95 syndromes
= (void *) __get_free_pages(GFP_KERNEL
, 1);
98 printk("raid6: Yikes! No memory available.\n");
102 dptrs
[disks
-2] = syndromes
;
103 dptrs
[disks
-1] = syndromes
+ PAGE_SIZE
;
105 bestperf
= 0; bestprefer
= 0; best
= NULL
;
107 for ( algo
= raid6_algos
; *algo
; algo
++ ) {
108 if ( !(*algo
)->valid
|| (*algo
)->valid() ) {
113 while ( (j1
= jiffies
) == j0
)
115 while (time_before(jiffies
,
116 j1
+ (1<<RAID6_TIME_JIFFIES_LG2
))) {
117 (*algo
)->gen_syndrome(disks
, PAGE_SIZE
, dptrs
);
122 if ( (*algo
)->prefer
> bestprefer
||
123 ((*algo
)->prefer
== bestprefer
&&
126 bestprefer
= best
->prefer
;
129 printk("raid6: %-8s %5ld MB/s\n", (*algo
)->name
,
130 (perf
*HZ
) >> (20-16+RAID6_TIME_JIFFIES_LG2
));
135 printk("raid6: using algorithm %s (%ld MB/s)\n",
137 (bestperf
*HZ
) >> (20-16+RAID6_TIME_JIFFIES_LG2
));
140 printk("raid6: Yikes! No algorithm found!\n");
142 free_pages((unsigned long)syndromes
, 1);
144 return best
? 0 : -EINVAL
;
147 static void raid6_exit(void)
152 subsys_initcall(raid6_select_algo
);
153 module_exit(raid6_exit
);
154 MODULE_LICENSE("GPL");
155 MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");