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-rw-r--r--lib/raid6/algos.c154
1 files changed, 154 insertions, 0 deletions
diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
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+/* -*- 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>
+#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");
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