Quelle xor.c Sprache: C

// 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;

#ifndef MODULE
static void __init do_xor_register(struct xor_block_template *tmpl)
{
tmpl->next = template_list;
template_list = tmpl;
}

static int __init register_xor_blocks(void)
{
active_template = XOR_SELECT_TEMPLATE(NULL);

if (!active_template) {
#define xor_speed do_xor_register
  // register all the templates and pick the first as the default
  XOR_TRY_TEMPLATES;
#undef xor_speed
  active_template = template_list;
}
return 0;
}
#endif

#define BENCH_SIZE 4096
#define REPS  800U

static void __init
do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
{
int speed;
unsigned long reps;
ktime_t min, start, t0;

tmpl->next = template_list;
template_list = tmpl;

preempt_disable();

reps = 0;
t0 = ktime_get();
/* delay start until time has advanced */
while ((start = ktime_get()) == t0)
  cpu_relax();
do {
  mb(); /* prevent loop optimization */
  tmpl->do_2(BENCH_SIZE, b1, b2);
  mb();
} while (reps++ < REPS || (t0 = ktime_get()) == start);
min = ktime_sub(t0, start);

preempt_enable();

// bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
speed = (1000 * reps * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);
tmpl->speed = speed;

pr_info(" %-16s: %5d MB/sec\n", tmpl->name, speed);
}

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");
template_list = NULL;
XOR_TRY_TEMPLATES;
fastest = template_list;
for (f = fastest; f; f = f->next)
  if (f->speed > fastest->speed)
   fastest = f;

pr_info("xor: using function: %s (%d MB/sec)\n",
        fastest->name, fastest->speed);

#undef xor_speed

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

static __exit void xor_exit(void) { }

MODULE_DESCRIPTION("RAID-5 checksumming functions");
MODULE_LICENSE("GPL");

#ifndef MODULE
/* when built-in xor.o must initialize before drivers/md/md.o */
core_initcall(register_xor_blocks);
#endif

module_init(calibrate_xor_blocks);
module_exit(xor_exit);

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