56a519913e
With CONFIG_PREEMPT=y, we need to disable preemption while benchmarking RAID5 xor checksumming to ensure we're actually measuring what we think we're measuring. Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com> Signed-off-by: NeilBrown <neilb@suse.de>
168 lines
4 KiB
C
168 lines
4 KiB
C
/*
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* xor.c : Multiple Devices driver for Linux
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*
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* Copyright (C) 1996, 1997, 1998, 1999, 2000,
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* Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
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*
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* Dispatch optimized RAID-5 checksumming functions.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* You should have received a copy of the GNU General Public License
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* (for example /usr/src/linux/COPYING); if not, write to the Free
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* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#define BH_TRACE 0
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#include <linux/module.h>
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#include <linux/gfp.h>
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#include <linux/raid/xor.h>
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#include <linux/jiffies.h>
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#include <linux/preempt.h>
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#include <asm/xor.h>
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/* The xor routines to use. */
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static struct xor_block_template *active_template;
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void
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xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
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{
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unsigned long *p1, *p2, *p3, *p4;
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p1 = (unsigned long *) srcs[0];
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if (src_count == 1) {
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active_template->do_2(bytes, dest, p1);
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return;
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}
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p2 = (unsigned long *) srcs[1];
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if (src_count == 2) {
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active_template->do_3(bytes, dest, p1, p2);
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return;
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}
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p3 = (unsigned long *) srcs[2];
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if (src_count == 3) {
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active_template->do_4(bytes, dest, p1, p2, p3);
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return;
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}
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p4 = (unsigned long *) srcs[3];
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active_template->do_5(bytes, dest, p1, p2, p3, p4);
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}
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EXPORT_SYMBOL(xor_blocks);
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/* Set of all registered templates. */
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static struct xor_block_template *template_list;
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#define BENCH_SIZE (PAGE_SIZE)
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static void
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do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
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{
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int speed;
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unsigned long now, j;
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int i, count, max;
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tmpl->next = template_list;
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template_list = tmpl;
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preempt_disable();
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/*
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* Count the number of XORs done during a whole jiffy, and use
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* this to calculate the speed of checksumming. We use a 2-page
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* allocation to have guaranteed color L1-cache layout.
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*/
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max = 0;
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for (i = 0; i < 5; i++) {
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j = jiffies;
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count = 0;
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while ((now = jiffies) == j)
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cpu_relax();
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while (time_before(jiffies, now + 1)) {
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mb(); /* prevent loop optimzation */
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tmpl->do_2(BENCH_SIZE, b1, b2);
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mb();
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count++;
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mb();
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}
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if (count > max)
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max = count;
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}
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preempt_enable();
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speed = max * (HZ * BENCH_SIZE / 1024);
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tmpl->speed = speed;
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printk(KERN_INFO " %-10s: %5d.%03d MB/sec\n", tmpl->name,
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speed / 1000, speed % 1000);
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}
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static int __init
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calibrate_xor_blocks(void)
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{
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void *b1, *b2;
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struct xor_block_template *f, *fastest;
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/*
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* Note: Since the memory is not actually used for _anything_ but to
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* test the XOR speed, we don't really want kmemcheck to warn about
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* reading uninitialized bytes here.
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*/
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b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 2);
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if (!b1) {
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printk(KERN_WARNING "xor: Yikes! No memory available.\n");
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return -ENOMEM;
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}
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b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
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/*
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* If this arch/cpu has a short-circuited selection, don't loop through
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* all the possible functions, just test the best one
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*/
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fastest = NULL;
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#ifdef XOR_SELECT_TEMPLATE
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fastest = XOR_SELECT_TEMPLATE(fastest);
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#endif
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#define xor_speed(templ) do_xor_speed((templ), b1, b2)
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if (fastest) {
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printk(KERN_INFO "xor: automatically using best "
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"checksumming function: %s\n",
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fastest->name);
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xor_speed(fastest);
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} else {
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printk(KERN_INFO "xor: measuring software checksum speed\n");
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XOR_TRY_TEMPLATES;
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fastest = template_list;
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for (f = fastest; f; f = f->next)
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if (f->speed > fastest->speed)
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fastest = f;
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}
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printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
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fastest->name, fastest->speed / 1000, fastest->speed % 1000);
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#undef xor_speed
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free_pages((unsigned long)b1, 2);
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active_template = fastest;
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return 0;
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}
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static __exit void xor_exit(void) { }
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MODULE_LICENSE("GPL");
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/* when built-in xor.o must initialize before drivers/md/md.o */
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core_initcall(calibrate_xor_blocks);
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module_exit(xor_exit);
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