On Fri, 2009-04-10 at 23:17 -0700, akpm@xxxxxxxxxxxxxxxxxxxx wrote:
> From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>
> In drv_read(), check to see whether we can run the rdmsr() on the current
> CPU. If so, do that. So smp_call_function_single() can avoid the IPI.
>
> Arguably, cpumask_any() should do this.
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
> Cc: Len Brown <len.brown@xxxxxxxxx>
> Cc: Zhao Yakui <yakui.zhao@xxxxxxxxx>
> Cc: Dave Jones <davej@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Tested-by: Mike Galbraith <efault@xxxxxx>
> Cc: "Zhang, Yanmin" <yanmin_zhang@xxxxxxxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
> arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff -puN arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c~arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c~arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts
> +++ a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> @@ -197,9 +197,22 @@ static void do_drv_write(void *_cmd)
>
> static void drv_read(struct drv_cmd *cmd)
> {
> - cmd->val = 0;
> + int target_cpu; /* The CPU on which to perform thr rdmsr() */
+ int target_cpu; /* The CPU on which to perform the rdmsr() */
--
JSR
--
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