Date: Sun, 2 Jul 2017 13:11:57 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Vikas Shivappa <vikas.shivappa@linux.intel.com>
cc: x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com,
        peterz@infradead.org, ravi.v.shankar@intel.com,
        vikas.shivappa@intel.com, tony.luck@intel.com, fenghua.yu@intel.com,
        andi.kleen@intel.com
Subject: Re: [PATCH 13/21] x86/intel_rdt/cqm: Add cpus file support
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References: <1498503368-20173-1-git-send-email-vikas.shivappa@linux.intel.com> <1498503368-20173-14-git-send-email-vikas.shivappa@linux.intel.com>
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On Mon, 26 Jun 2017, Vikas Shivappa wrote:
> diff --git a/arch/x86/kernel/cpu/intel_rdt.h b/arch/x86/kernel/cpu/intel_rdt.h
> index fdf3654..fec8ba9 100644
> --- a/arch/x86/kernel/cpu/intel_rdt.h
> +++ b/arch/x86/kernel/cpu/intel_rdt.h
> @@ -37,6 +37,8 @@ struct mon_evt {
>  extern bool rdt_alloc_enabled;
>  extern int rdt_mon_features;
>  
> +DECLARE_PER_CPU_READ_MOSTLY(int, cpu_rmid);

u32

>  
> +DEFINE_PER_CPU_READ_MOSTLY(int, cpu_rmid);
>  static inline struct rmid_entry *__rmid_entry(u32 rmid)

Bah. Please add a new line between the DEFINE... and the function.

But that whole thing is wrong. The per cpu default closid and rmid want to
be in a single place, not in two distinct per cpu variables.

struct rdt_cpu_default {
       u32	rmid;
       u32	closid;
};

DEFINE_PER_CPU_READ_MOSTLY(struct rdt_cpu_default, rdt_cpu_default);

or something like this. That way it's guaranteed that the context switch
code touches a single cache line for the per cpu defaults.

Thanks,

	tglx