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Commit 01599fca authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

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 6b44003e
  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: default avatarDave Jones <davej@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarMike Galbraith <efault@gmx.de>
Cc: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Acked-by: default avatarIngo 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8371f87c

arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c

+9 −15
Original line number Diff line number Diff line
@@ -153,7 +153,8 @@ struct drv_cmd { 
	u32 val;

};



static long do_drv_read(void *_cmd)

/* Called via smp_call_function_single(), on the target CPU */

static void do_drv_read(void *_cmd)

{

	struct drv_cmd *cmd = _cmd;

	u32 h;
@@ -170,10 +171,10 @@ static long do_drv_read(void *_cmd) 
	default:

		break;

	}

	return 0;

}



static long do_drv_write(void *_cmd)

/* Called via smp_call_function_many(), on the target CPUs */

static void do_drv_write(void *_cmd)

{

	struct drv_cmd *cmd = _cmd;

	u32 lo, hi;
@@ -192,23 +193,18 @@ static long do_drv_write(void *_cmd) 
	default:

		break;

	}

	return 0;

}



static void drv_read(struct drv_cmd *cmd)

{

	cmd->val = 0;



	work_on_cpu(cpumask_any(cmd->mask), do_drv_read, cmd);

	smp_call_function_single(cpumask_any(cmd->mask), do_drv_read, cmd, 1);

}



static void drv_write(struct drv_cmd *cmd)

{

	unsigned int i;



	for_each_cpu(i, cmd->mask) {

		work_on_cpu(i, do_drv_write, cmd);

	}

	smp_call_function_many(cmd->mask, do_drv_write, cmd, 1);

}



static u32 get_cur_val(const struct cpumask *mask)
@@ -252,15 +248,13 @@ struct perf_pair { 
	} aperf, mperf;

};





static long read_measured_perf_ctrs(void *_cur)

/* Called via smp_call_function_single(), on the target CPU */

static void read_measured_perf_ctrs(void *_cur)

{

	struct perf_pair *cur = _cur;



	rdmsr(MSR_IA32_APERF, cur->aperf.split.lo, cur->aperf.split.hi);

	rdmsr(MSR_IA32_MPERF, cur->mperf.split.lo, cur->mperf.split.hi);



	return 0;

}



/*
@@ -283,7 +277,7 @@ static unsigned int get_measured_perf(struct cpufreq_policy *policy, 
	unsigned int perf_percent;

	unsigned int retval;



	if (!work_on_cpu(cpu, read_measured_perf_ctrs, &readin))

	if (smp_call_function_single(cpu, read_measured_perf_ctrs, &cur, 1))

		return 0;



	cur.aperf.whole = readin.aperf.whole -