FreeBSD/Linux Kernel Cross Reference
sys/crypto/xor.c

     /*
      * 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.
      *
      * This program is free software; you can redistribute it and/or modify
     * it under the terms of the GNU General Public License as published by
     * the Free Software Foundation; either version 2, or (at your option)
     * any later version.
     *
     * You should have received a copy of the GNU General Public License
     * (for example /usr/src/linux/COPYING); if not, write to the Free
     * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
     */
    
    #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>
    
    /* 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;
   
           /*
            * Note: Since the memory is not actually used for _anything_ but to
            * test the XOR speed, we don't really want kmemcheck to warn about
            * reading uninitialized bytes here.
            */
           b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 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
            */
   
           fastest = NULL;
   
   #ifdef XOR_SELECT_TEMPLATE
                   fastest = XOR_SELECT_TEMPLATE(fastest);
   #endif
   
   #define xor_speed(templ)        do_xor_speed((templ), b1, b2)
   
           if (fastest) {
                   printk(KERN_INFO "xor: automatically using best "
                                    "checksumming function:\n");
                   xor_speed(fastest);
                   goto out;
           } else {
                   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
   
    out:
           free_pages((unsigned long)b1, 2);
   
           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);

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