linux-kernel - Re: [PATCH] trace power_frequency events on the correct cpu (for Intel x86 CPUs)

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Date:	Fri, 12 Mar 2010 06:52:29 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Robert Schöne <robert.schoene@...dresden.de>
CC:	Dave Jones <davej@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	cpufreq <cpufreq@...r.kernel.org>, x86@...nel.org
Subject: Re: [PATCH] trace power_frequency events on the correct cpu  (for
 Intel x86 CPUs)

On 3/12/2010 5:17, Robert Schöne wrote:
> This patch fixes the following behaviour:
> Currently, the power_frequency event is reported for the cpu (core) which initiated the frequency change.
> It should be reported for the cpu that actually changes its frequency.
>
> Example: when using
>   taskset -c 0 echo<new_frequency>  >  /sys/devices/system/cpu/cpu1/cpufreq/scaling_setspeed
> cpu 0 is traced, instead of cpu 1
>
> Signed of by Robert Schoene<robert.schoene@...dresden.de>
>
>
> diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> index 1b1920f..0a47f10 100644
> --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> +++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> @@ -174,6 +174,7 @@ static void do_drv_write(void *_cmd)
>
>          switch (cmd->type) {
>          case SYSTEM_INTEL_MSR_CAPABLE:
> +               trace_power_frequency(POWER_PSTATE, cmd->val);
>                  rdmsr(cmd->addr.msr.reg, lo, hi);
>                  lo = (lo&  ~INTEL_MSR_RANGE) | (cmd->val&  INTEL_MSR_RANGE);
>                  wrmsr(cmd->addr.msr.reg, lo, hi);
> @@ -363,7 +364,6 @@ static int acpi_cpufreq_target(struct cpufreq_policy *policy,
>                  }
>          }
>
> -       trace_power_frequency(POWER_PSTATE, data->freq_table[next_state].frequency);
>
>          switch (data->cpu_feature) {
>          case SYSTEM_INTEL_MSR_CAPABLE:
>
>

are you sure this is right?
it's moving something from outside a switch statement to inside only one prong of a switch statement...

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