Root/crypto/xor.c

1/*
2 * xor.c : Multiple Devices driver for Linux
3 *
4 * Copyright (C) 1996, 1997, 1998, 1999, 2000,
5 * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
6 *
7 * Dispatch optimized RAID-5 checksumming functions.
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2, or (at your option)
12 * any later version.
13 *
14 * You should have received a copy of the GNU General Public License
15 * (for example /usr/src/linux/COPYING); if not, write to the Free
16 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19#define BH_TRACE 0
20#include <linux/module.h>
21#include <linux/gfp.h>
22#include <linux/raid/xor.h>
23#include <linux/jiffies.h>
24#include <linux/preempt.h>
25#include <asm/xor.h>
26
27/* The xor routines to use. */
28static struct xor_block_template *active_template;
29
30void
31xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
32{
33    unsigned long *p1, *p2, *p3, *p4;
34
35    p1 = (unsigned long *) srcs[0];
36    if (src_count == 1) {
37        active_template->do_2(bytes, dest, p1);
38        return;
39    }
40
41    p2 = (unsigned long *) srcs[1];
42    if (src_count == 2) {
43        active_template->do_3(bytes, dest, p1, p2);
44        return;
45    }
46
47    p3 = (unsigned long *) srcs[2];
48    if (src_count == 3) {
49        active_template->do_4(bytes, dest, p1, p2, p3);
50        return;
51    }
52
53    p4 = (unsigned long *) srcs[3];
54    active_template->do_5(bytes, dest, p1, p2, p3, p4);
55}
56EXPORT_SYMBOL(xor_blocks);
57
58/* Set of all registered templates. */
59static struct xor_block_template *__initdata template_list;
60
61#define BENCH_SIZE (PAGE_SIZE)
62
63static void __init
64do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
65{
66    int speed;
67    unsigned long now, j;
68    int i, count, max;
69
70    tmpl->next = template_list;
71    template_list = tmpl;
72
73    preempt_disable();
74
75    /*
76     * Count the number of XORs done during a whole jiffy, and use
77     * this to calculate the speed of checksumming. We use a 2-page
78     * allocation to have guaranteed color L1-cache layout.
79     */
80    max = 0;
81    for (i = 0; i < 5; i++) {
82        j = jiffies;
83        count = 0;
84        while ((now = jiffies) == j)
85            cpu_relax();
86        while (time_before(jiffies, now + 1)) {
87            mb(); /* prevent loop optimzation */
88            tmpl->do_2(BENCH_SIZE, b1, b2);
89            mb();
90            count++;
91            mb();
92        }
93        if (count > max)
94            max = count;
95    }
96
97    preempt_enable();
98
99    speed = max * (HZ * BENCH_SIZE / 1024);
100    tmpl->speed = speed;
101
102    printk(KERN_INFO " %-10s: %5d.%03d MB/sec\n", tmpl->name,
103           speed / 1000, speed % 1000);
104}
105
106static int __init
107calibrate_xor_blocks(void)
108{
109    void *b1, *b2;
110    struct xor_block_template *f, *fastest;
111
112    /*
113     * Note: Since the memory is not actually used for _anything_ but to
114     * test the XOR speed, we don't really want kmemcheck to warn about
115     * reading uninitialized bytes here.
116     */
117    b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 2);
118    if (!b1) {
119        printk(KERN_WARNING "xor: Yikes! No memory available.\n");
120        return -ENOMEM;
121    }
122    b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
123
124    /*
125     * If this arch/cpu has a short-circuited selection, don't loop through
126     * all the possible functions, just test the best one
127     */
128
129    fastest = NULL;
130
131#ifdef XOR_SELECT_TEMPLATE
132        fastest = XOR_SELECT_TEMPLATE(fastest);
133#endif
134
135#define xor_speed(templ) do_xor_speed((templ), b1, b2)
136
137    if (fastest) {
138        printk(KERN_INFO "xor: automatically using best "
139                 "checksumming function:\n");
140        xor_speed(fastest);
141        goto out;
142    } else {
143        printk(KERN_INFO "xor: measuring software checksum speed\n");
144        XOR_TRY_TEMPLATES;
145        fastest = template_list;
146        for (f = fastest; f; f = f->next)
147            if (f->speed > fastest->speed)
148                fastest = f;
149    }
150
151    printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
152           fastest->name, fastest->speed / 1000, fastest->speed % 1000);
153
154#undef xor_speed
155
156 out:
157    free_pages((unsigned long)b1, 2);
158
159    active_template = fastest;
160    return 0;
161}
162
163static __exit void xor_exit(void) { }
164
165MODULE_LICENSE("GPL");
166
167/* when built-in xor.o must initialize before drivers/md/md.o */
168core_initcall(calibrate_xor_blocks);
169module_exit(xor_exit);
170

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