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Revision 01599fca6758d2cd133e78f87426fc851c9ea725 authored by Andrew Morton on 13 April 2009, 17:27:49 UTC, committed by Linus Torvalds on 13 April 2009, 18:09:46 UTC 
cpufreq: use smp_call_function_[single|many]() in acpi-cpufreq.c
 
Atttempting to rid us of the problematic work_on_cpu().  Just use
smp_call_fuction_single() here.

This repairs a 10% sysbench(oltp)+mysql regression which Mike reported,
due to

  commit 6b44003e5ca66a3fffeb5bc90f40ada2c4340896
  Author: Andrew Morton <akpm@linux-foundation.org>
  Date:   Thu Apr 9 09:50:37 2009 -0600

      work_on_cpu(): rewrite it to create a kernel thread on demand

It seems that the kernel calls these acpi-cpufreq functions at a quite
high frequency.

Valdis Kletnieks also reports that this causes 70-90 forks per second on
his hardware.

Cc: Valdis.Kletnieks@vt.edu
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Zhao Yakui <yakui.zhao@intel.com>
Acked-by: Dave Jones <davej@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mike Galbraith <efault@gmx.de>
Cc: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
[ Made it use smp_call_function_many() instead of looping over cpu's
  with smp_call_function_single()    - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 8371f87
Raw File
libcrc32c.c 
/* 
 * CRC32C
 *@Article{castagnoli-crc,
 * author =       { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
 * title =        {{Optimization of Cyclic Redundancy-Check Codes with 24
 *                 and 32 Parity Bits}},
 * journal =      IEEE Transactions on Communication,
 * year =         {1993},
 * volume =       {41},
 * number =       {6},
 * pages =        {},
 * month =        {June},
 *}
 * Used by the iSCSI driver, possibly others, and derived from the
 * the iscsi-crc.c module of the linux-iscsi driver at
 * http://linux-iscsi.sourceforge.net.
 *
 * Following the example of lib/crc32, this function is intended to be
 * flexible and useful for all users.  Modules that currently have their
 * own crc32c, but hopefully may be able to use this one are:
 *  net/sctp (please add all your doco to here if you change to
 *            use this one!)
 *  <endoflist>
 *
 * Copyright (c) 2004 Cisco Systems, Inc.
 * 
 * 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 of the License, or (at your option) 
 * any later version.
 *
 */

#include <crypto/hash.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

static struct crypto_shash *tfm;

u32 crc32c(u32 crc, const void *address, unsigned int length)
{
	struct {
		struct shash_desc shash;
		char ctx[crypto_shash_descsize(tfm)];
	} desc;
	int err;

	desc.shash.tfm = tfm;
	desc.shash.flags = 0;
	*(u32 *)desc.ctx = crc;

	err = crypto_shash_update(&desc.shash, address, length);
	BUG_ON(err);

	return *(u32 *)desc.ctx;
}

EXPORT_SYMBOL(crc32c);

static int __init libcrc32c_mod_init(void)
{
	tfm = crypto_alloc_shash("crc32c", 0, 0);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	return 0;
}

static void __exit libcrc32c_mod_fini(void)
{
	crypto_free_shash(tfm);
}

module_init(libcrc32c_mod_init);
module_exit(libcrc32c_mod_fini);

MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations");
MODULE_LICENSE("GPL");
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