aboutsummaryrefslogtreecommitdiff
path: root/crypto/xor.c
blob: ea7349e6ed23b83a2f4b5f4c85b4ee50965254ee (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * xor.c : Multiple Devices driver for Linux
 *
 * Copyright (C) 1996, 1997, 1998, 1999, 2000,
 * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
 *
 * Dispatch optimized RAID-5 checksumming functions.
 */

#define BH_TRACE 0
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/raid/xor.h>
#include <linux/jiffies.h>
#include <linux/preempt.h>
#include <asm/xor.h>

#ifndef XOR_SELECT_TEMPLATE
#define XOR_SELECT_TEMPLATE(x) (x)
#endif

/* The xor routines to use.  */
static struct xor_block_template *active_template;

void
xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
{
	unsigned long *p1, *p2, *p3, *p4;

	p1 = (unsigned long *) srcs[0];
	if (src_count == 1) {
		active_template->do_2(bytes, dest, p1);
		return;
	}

	p2 = (unsigned long *) srcs[1];
	if (src_count == 2) {
		active_template->do_3(bytes, dest, p1, p2);
		return;
	}

	p3 = (unsigned long *) srcs[2];
	if (src_count == 3) {
		active_template->do_4(bytes, dest, p1, p2, p3);
		return;
	}

	p4 = (unsigned long *) srcs[3];
	active_template->do_5(bytes, dest, p1, p2, p3, p4);
}
EXPORT_SYMBOL(xor_blocks);

/* Set of all registered templates.  */
static struct xor_block_template *__initdata template_list;

#define BENCH_SIZE (PAGE_SIZE)

static void __init
do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
{
	int speed;
	unsigned long now, j;
	int i, count, max;

	tmpl->next = template_list;
	template_list = tmpl;

	preempt_disable();

	/*
	 * Count the number of XORs done during a whole jiffy, and use
	 * this to calculate the speed of checksumming.  We use a 2-page
	 * allocation to have guaranteed color L1-cache layout.
	 */
	max = 0;
	for (i = 0; i < 5; i++) {
		j = jiffies;
		count = 0;
		while ((now = jiffies) == j)
			cpu_relax();
		while (time_before(jiffies, now + 1)) {
			mb(); /* prevent loop optimzation */
			tmpl->do_2(BENCH_SIZE, b1, b2);
			mb();
			count++;
			mb();
		}
		if (count > max)
			max = count;
	}

	preempt_enable();

	speed = max * (HZ * BENCH_SIZE / 1024);
	tmpl->speed = speed;

	printk(KERN_INFO "   %-10s: %5d.%03d MB/sec\n", tmpl->name,
	       speed / 1000, speed % 1000);
}

static int __init
calibrate_xor_blocks(void)
{
	void *b1, *b2;
	struct xor_block_template *f, *fastest;

	fastest = XOR_SELECT_TEMPLATE(NULL);

	if (fastest) {
		printk(KERN_INFO "xor: automatically using best "
				 "checksumming function   %-10s\n",
		       fastest->name);
		goto out;
	}

	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
	if (!b1) {
		printk(KERN_WARNING "xor: Yikes!  No memory available.\n");
		return -ENOMEM;
	}
	b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;

	/*
	 * If this arch/cpu has a short-circuited selection, don't loop through
	 * all the possible functions, just test the best one
	 */

#define xor_speed(templ)	do_xor_speed((templ), b1, b2)

	printk(KERN_INFO "xor: measuring software checksum speed\n");
	XOR_TRY_TEMPLATES;
	fastest = template_list;
	for (f = fastest; f; f = f->next)
		if (f->speed > fastest->speed)
			fastest = f;

	printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
	       fastest->name, fastest->speed / 1000, fastest->speed % 1000);

#undef xor_speed

	free_pages((unsigned long)b1, 2);
out:
	active_template = fastest;
	return 0;
}

static __exit void xor_exit(void) { }

MODULE_LICENSE("GPL");

/* when built-in xor.o must initialize before drivers/md/md.o */
core_initcall(calibrate_xor_blocks);
module_exit(xor_exit);