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 #ifndef XOR_SELECT_TEMPLATE
28 #define XOR_SELECT_TEMPLATE(x) (x)
29 #endif
30 
31 /* The xor routines to use.  */
32 static struct xor_block_template *active_template;
33 
34 void
xor_blocks(unsigned int src_count,unsigned int bytes,void * dest,void ** srcs)35 xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
36 {
37 	unsigned long *p1, *p2, *p3, *p4;
38 
39 	p1 = (unsigned long *) srcs[0];
40 	if (src_count == 1) {
41 		active_template->do_2(bytes, dest, p1);
42 		return;
43 	}
44 
45 	p2 = (unsigned long *) srcs[1];
46 	if (src_count == 2) {
47 		active_template->do_3(bytes, dest, p1, p2);
48 		return;
49 	}
50 
51 	p3 = (unsigned long *) srcs[2];
52 	if (src_count == 3) {
53 		active_template->do_4(bytes, dest, p1, p2, p3);
54 		return;
55 	}
56 
57 	p4 = (unsigned long *) srcs[3];
58 	active_template->do_5(bytes, dest, p1, p2, p3, p4);
59 }
60 EXPORT_SYMBOL(xor_blocks);
61 
62 /* Set of all registered templates.  */
63 static struct xor_block_template *__initdata template_list;
64 
65 #define BENCH_SIZE (PAGE_SIZE)
66 
67 static void __init
do_xor_speed(struct xor_block_template * tmpl,void * b1,void * b2)68 do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
69 {
70 	int speed;
71 	unsigned long now, j;
72 	int i, count, max;
73 
74 	tmpl->next = template_list;
75 	template_list = tmpl;
76 
77 	preempt_disable();
78 
79 	/*
80 	 * Count the number of XORs done during a whole jiffy, and use
81 	 * this to calculate the speed of checksumming.  We use a 2-page
82 	 * allocation to have guaranteed color L1-cache layout.
83 	 */
84 	max = 0;
85 	for (i = 0; i < 5; i++) {
86 		j = jiffies;
87 		count = 0;
88 		while ((now = jiffies) == j)
89 			cpu_relax();
90 		while (time_before(jiffies, now + 1)) {
91 			mb(); /* prevent loop optimzation */
92 			tmpl->do_2(BENCH_SIZE, b1, b2);
93 			mb();
94 			count++;
95 			mb();
96 		}
97 		if (count > max)
98 			max = count;
99 	}
100 
101 	preempt_enable();
102 
103 	speed = max * (HZ * BENCH_SIZE / 1024);
104 	tmpl->speed = speed;
105 
106 	printk(KERN_INFO "   %-10s: %5d.%03d MB/sec\n", tmpl->name,
107 	       speed / 1000, speed % 1000);
108 }
109 
110 static int __init
calibrate_xor_blocks(void)111 calibrate_xor_blocks(void)
112 {
113 	void *b1, *b2;
114 	struct xor_block_template *f, *fastest;
115 
116 	fastest = XOR_SELECT_TEMPLATE(NULL);
117 
118 	if (fastest) {
119 		printk(KERN_INFO "xor: automatically using best "
120 				 "checksumming function   %-10s\n",
121 		       fastest->name);
122 		goto out;
123 	}
124 
125 	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
126 	if (!b1) {
127 		printk(KERN_WARNING "xor: Yikes!  No memory available.\n");
128 		return -ENOMEM;
129 	}
130 	b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
131 
132 	/*
133 	 * If this arch/cpu has a short-circuited selection, don't loop through
134 	 * all the possible functions, just test the best one
135 	 */
136 
137 #define xor_speed(templ)	do_xor_speed((templ), b1, b2)
138 
139 	printk(KERN_INFO "xor: measuring software checksum speed\n");
140 	XOR_TRY_TEMPLATES;
141 	fastest = template_list;
142 	for (f = fastest; f; f = f->next)
143 		if (f->speed > fastest->speed)
144 			fastest = f;
145 
146 	printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
147 	       fastest->name, fastest->speed / 1000, fastest->speed % 1000);
148 
149 #undef xor_speed
150 
151 	free_pages((unsigned long)b1, 2);
152 out:
153 	active_template = fastest;
154 	return 0;
155 }
156 
xor_exit(void)157 static __exit void xor_exit(void) { }
158 
159 MODULE_LICENSE("GPL");
160 
161 /* when built-in xor.o must initialize before drivers/md/md.o */
162 core_initcall(calibrate_xor_blocks);
163 module_exit(xor_exit);
164