linux-kernel - Re: [RFC] Extend mwait idle to optimize away IPIs when possible

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Date:	Mon, 06 Feb 2012 16:26:23 -0800
From:	David Daney <david.daney@...ium.com>
To:	Venkatesh Pallipadi <venki@...gle.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Aaron Durbin <adurbin@...gle.com>,
	Paul Turner <pjt@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC] Extend mwait idle to optimize away IPIs when possible

On 02/06/2012 12:42 PM, Venkatesh Pallipadi wrote:
[...]
> index 5bed94e..6a56cb0 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -170,6 +170,11 @@ config GENERIC_TIME_VSYSCALL
>   	bool
>   	default X86_64
>
> +config AVOID_IPI_ON_IDLE
> +	bool
> +	depends on X86_64
> +	default X86_64
> +

Can you get rid of this part...

>   config ARCH_HAS_CPU_RELAX
>   	def_bool y
>
[...]
> diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
> index f50e7fb..340c4e9 100644
> --- a/arch/x86/kernel/acpi/cstate.c
> +++ b/arch/x86/kernel/acpi/cstate.c
> @@ -161,6 +161,14 @@ EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);
>    */
>   void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
>   {
> +#ifdef CONFIG_AVOID_IPI_ON_IDLE


... and change all of these to #ifdef CONFIG_64BIT

> +	int oldval, cpu = smp_processor_id();
> +
.
.
.

Thanks,
David Daney
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