/* -*- linux-c -*- ------------------------------------------------------- *
*
* Copyright 2002 H. Peter Anvin - All Rights Reserved
*
* 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, Inc., 53 Temple Place Ste 330,
* Boston MA 02111-1307, USA; either version 2 of the License, or
* (at your option) any later version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* raid6/algos.c
*
* Algorithm list and algorithm selection for RAID-6
*/
#include <linux/raid/pq.h>
#include <linux/module.h>
#ifndef __KERNEL__
#include <sys/mman.h>
#include <stdio.h>
#else
#include <linux/gfp.h>
#if !RAID6_USE_EMPTY_ZERO_PAGE
/* In .bss so it's zeroed */
const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
EXPORT_SYMBOL(raid6_empty_zero_page);
#endif
#endif
struct raid6_calls raid6_call;
EXPORT_SYMBOL_GPL(raid6_call);
const struct raid6_calls * const raid6_algos[] = {
&raid6_intx1,
&raid6_intx2,
&raid6_intx4,
&raid6_intx8,
#if defined(__ia64__)
&raid6_intx16,
&raid6_intx32,
#endif
#if defined(__i386__) && !defined(__arch_um__)
&raid6_mmxx1,
&raid6_mmxx2,
&raid6_sse1x1,
&raid6_sse1x2,
&raid6_sse2x1,
&raid6_sse2x2,
#endif
#if defined(__x86_64__) && !defined(__arch_um__)
&raid6_sse2x1,
&raid6_sse2x2,
&raid6_sse2x4,
#endif
#ifdef CONFIG_ALTIVEC
&raid6_altivec1,
&raid6_altivec2,
&raid6_altivec4,
&raid6_altivec8,
#endif
NULL
};
#ifdef __KERNEL__
#define RAID6_TIME_JIFFIES_LG2 4
#else
/* Need more time to be stable in userspace */
#define RAID6_TIME_JIFFIES_LG2 9
#define time_before(x, y) ((x) < (y))
#endif
/* Try to pick the best algorithm */
/* This code uses the gfmul table as convenient data set to abuse */
int __init raid6_select_algo(void)
{
const struct raid6_calls * const * algo;
const struct raid6_calls * best;
char *syndromes;
void *dptrs[(65536/PAGE_SIZE)+2];
int i, disks;
unsigned long perf, bestperf;
int bestprefer;
unsigned long j0, j1;
disks = (65536/PAGE_SIZE)+2;
for ( i = 0 ; i < disks-2 ; i++ ) {
dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
}
/* Normal code - use a 2-page allocation to avoid D$ conflict */
syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
if ( !syndromes ) {
printk("raid6: Yikes! No memory available.\n");
return -ENOMEM;
}
dptrs[disks-2] = syndromes;
dptrs[disks-1] = syndromes + PAGE_SIZE;
bestperf = 0; bestprefer = 0; best = NULL;
for ( algo = raid6_algos ; *algo ; algo++ ) {
if ( !(*algo)->valid || (*algo)->valid() ) {
perf = 0;
preempt_disable();
j0 = jiffies;
while ( (j1 = jiffies) == j0 )
cpu_relax();
while (time_before(jiffies,
j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
(*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
perf++;
}
preempt_enable();
if ( (*algo)->prefer > bestprefer ||
((*algo)->prefer == bestprefer &&
perf > bestperf) ) {
best = *algo;
bestprefer = best->prefer;
bestperf = perf;
}
printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
(perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
}
}
if (best) {
printk("raid6: using algorithm %s (%ld MB/s)\n",
best->name,
(bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
raid6_call = *best;
} else
printk("raid6: Yikes! No algorithm found!\n");
free_pages((unsigned long)syndromes, 1);
return best ? 0 : -EINVAL;
}
static void raid6_exit(void)
{
do { } while (0);
}
subsys_initcall(raid6_select_algo);
module_exit(raid6_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");
