linux-kernel - Re: [PATCH 05/32] x86/intel_rdt: Implement scheduling support for Intel RDT

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Date:	Mon, 25 Jul 2016 11:25:10 -0500
From:	Nilay Vaish <nilayvaish@...il.com>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	Tony Luck <tony.luck@...el.com>, Tejun Heo <tj@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Stephane Eranian <eranian@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	David Carrillo-Cisneros <davidcc@...gle.com>,
	Ravi V Shankar <ravi.v.shankar@...el.com>,
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	Sai Prakhya <sai.praneeth.prakhya@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH 05/32] x86/intel_rdt: Implement scheduling support for
 Intel RDT

On 12 July 2016 at 20:02, Fenghua Yu <fenghua.yu@...el.com> wrote:
> diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
> index 4f45dc8..afb6da3 100644
> --- a/arch/x86/include/asm/intel_rdt.h
> +++ b/arch/x86/include/asm/intel_rdt.h
> @@ -3,14 +3,42 @@
>
>  #ifdef CONFIG_INTEL_RDT
>
> +#include <linux/jump_label.h>
> +
>  #define MAX_CBM_LENGTH                 32
>  #define IA32_L3_CBM_BASE               0xc90
>  #define CBM_FROM_INDEX(x)              (IA32_L3_CBM_BASE + x)
>
> +extern struct static_key rdt_enable_key;
> +void __intel_rdt_sched_in(void *dummy);
> +
>  struct clos_cbm_table {
>         unsigned long l3_cbm;
>         unsigned int clos_refcnt;
>  };
>
> +/*
> + * intel_rdt_sched_in() - Writes the task's CLOSid to IA32_PQR_MSR
> + *
> + * Following considerations are made so that this has minimal impact
> + * on scheduler hot path:
> + * - This will stay as no-op unless we are running on an Intel SKU
> + * which supports L3 cache allocation.
> + * - Caches the per cpu CLOSid values and does the MSR write only
> + * when a task with a different CLOSid is scheduled in.
> + */
> +static inline void intel_rdt_sched_in(void)
> +{
> +       /*
> +        * Call the schedule in code only when RDT is enabled.
> +        */
> +       if (static_key_false(&rdt_enable_key))
> +               __intel_rdt_sched_in(NULL);

static_key_false() is deprecated.  I think this should be
static_branch_unlikely().

> diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
> index 6ad5b48..8379df8 100644
> --- a/arch/x86/kernel/cpu/intel_rdt.c
> +++ b/arch/x86/kernel/cpu/intel_rdt.c
> @@ -44,12 +46,33 @@ static cpumask_t rdt_cpumask;
>   */
>  static cpumask_t tmp_cpumask;
>  static DEFINE_MUTEX(rdt_group_mutex);
> +struct static_key __read_mostly rdt_enable_key = STATIC_KEY_INIT_FALSE;
>

Similarly, this should be DEFINE_STATIC_KEY_FALSE(rdt_enable_key);


Thanks
Nilay