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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/raid/md.h>
#include <linux/raid/xor.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 *template_list;

#define BENCH_SIZE (PAGE_SIZE)

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

      tmpl->next = template_list;
      template_list = tmpl;

      /*
       * 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++) {
            now = jiffies;
            count = 0;
            while (jiffies == now) {
                  mb(); /* prevent loop optimzation */
                  tmpl->do_2(BENCH_SIZE, b1, b2);
                  mb();
                  count++;
                  mb();
            }
            if (count > max)
                  max = count;
      }

      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;

      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
       */

      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: %s\n",
                  fastest->name);
            xor_speed(fastest);
      } 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

      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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