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");
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