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Linux/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 #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
 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
 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
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         /*
126          * Note: Since the memory is not actually used for _anything_ but to
127          * test the XOR speed, we don't really want kmemcheck to warn about
128          * reading uninitialized bytes here.
129          */
130         b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 2);
131         if (!b1) {
132                 printk(KERN_WARNING "xor: Yikes!  No memory available.\n");
133                 return -ENOMEM;
134         }
135         b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
136 
137         /*
138          * If this arch/cpu has a short-circuited selection, don't loop through
139          * all the possible functions, just test the best one
140          */
141 
142 #define xor_speed(templ)        do_xor_speed((templ), b1, b2)
143 
144         printk(KERN_INFO "xor: measuring software checksum speed\n");
145         XOR_TRY_TEMPLATES;
146         fastest = template_list;
147         for (f = fastest; f; f = f->next)
148                 if (f->speed > fastest->speed)
149                         fastest = f;
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         free_pages((unsigned long)b1, 2);
157 out:
158         active_template = fastest;
159         return 0;
160 }
161 
162 static __exit void xor_exit(void) { }
163 
164 MODULE_LICENSE("GPL");
165 
166 /* when built-in xor.o must initialize before drivers/md/md.o */
167 core_initcall(calibrate_xor_blocks);
168 module_exit(xor_exit);
169 

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