linux-kernel - Re: [PATCH] Don't export sched_mc_power

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Message-ID: <20081130174034.GA28614@elte.hu>
Date:	Sun, 30 Nov 2008 18:40:34 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] Don't export sched_mc_power_savings in laptops


* Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com> wrote:

>         Fix to prevent sched_mc_power_saving from being exported through sysfs
>         for multicore single socket (Laptop).
>     
>         CPU core map of the boot cpu should be equal to possible number
>         of cpus for single socket system.
>     
>         This fix has been developed at FOSS.in kernel workout.
>     
>         Signed-off-by: Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>
> 
> diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
> index 4850e4b..4adc830 100644
> --- a/arch/x86/include/asm/topology.h
> +++ b/arch/x86/include/asm/topology.h
> @@ -239,7 +239,7 @@ struct pci_bus;
>  void set_pci_bus_resources_arch_default(struct pci_bus *b);
>  
>  #ifdef CONFIG_SMP
> -#define mc_capable()			(boot_cpu_data.x86_max_cores > 1)
> +#define mc_capable()	(cpus_weight(per_cpu(cpu_core_map,0)) != nr_cpu_ids)

hm, dunno. sched_mc_power_savings should have no effect on single-socket 
systems, right? So the knob should have no effect.

	Ingo
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