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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
ratelimit.c 
/*
 * ratelimit.c - Do something with rate limit.
 *
 * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
 *
 * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
 * parameter. Now every user can use their own standalone ratelimit_state.
 *
 * This file is released under the GPLv2.
 *
 */

#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/module.h>

static DEFINE_SPINLOCK(ratelimit_lock);

/*
 * __ratelimit - rate limiting
 * @rs: ratelimit_state data
 *
 * This enforces a rate limit: not more than @rs->ratelimit_burst callbacks
 * in every @rs->ratelimit_jiffies
 */
int __ratelimit(struct ratelimit_state *rs)
{
	unsigned long flags;

	if (!rs->interval)
		return 1;

	spin_lock_irqsave(&ratelimit_lock, flags);
	if (!rs->begin)
		rs->begin = jiffies;

	if (time_is_before_jiffies(rs->begin + rs->interval)) {
		if (rs->missed)
			printk(KERN_WARNING "%s: %d callbacks suppressed\n",
				__func__, rs->missed);
		rs->begin = 0;
		rs->printed = 0;
		rs->missed = 0;
	}
	if (rs->burst && rs->burst > rs->printed)
		goto print;

	rs->missed++;
	spin_unlock_irqrestore(&ratelimit_lock, flags);
	return 0;

print:
	rs->printed++;
	spin_unlock_irqrestore(&ratelimit_lock, flags);
	return 1;
}
EXPORT_SYMBOL(__ratelimit);
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