linux-kernel - Re: [PATCH 7/9] x86/intel_rdt: Implement scheduling support for Intel RDT

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Date:	Wed, 29 Jul 2015 15:49:59 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, vikas.shivappa@...el.com,
	x86@...nel.org, hpa@...or.com, tglx@...utronix.de,
	mingo@...nel.org, tj@...nel.org, matt.fleming@...el.com,
	will.auld@...el.com, glenn.p.williamson@...el.com,
	kanaka.d.juvva@...el.com
Subject: Re: [PATCH 7/9] x86/intel_rdt: Implement scheduling support for
 Intel RDT

On Wed, Jul 01, 2015 at 03:21:08PM -0700, Vikas Shivappa wrote:
> diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
> index 3ad426c..78df3d7 100644
> --- a/arch/x86/include/asm/intel_rdt.h
> +++ b/arch/x86/include/asm/intel_rdt.h
> @@ -4,10 +4,16 @@
>  #ifdef CONFIG_CGROUP_RDT
>  
>  #include <linux/cgroup.h>
> +#include <asm/rdt_common.h>
> +
>  #define MAX_CBM_LENGTH			32
>  #define IA32_L3_CBM_BASE		0xc90
>  #define CBM_FROM_INDEX(x)		(IA32_L3_CBM_BASE + x)
>  
> +DECLARE_PER_CPU(struct intel_pqr_state, pqr_state);

You don't think this should be in rdt_common.h ?

> diff --git a/arch/x86/include/asm/rdt_common.h b/arch/x86/include/asm/rdt_common.h
> new file mode 100644
> index 0000000..01502c5
> --- /dev/null
> +++ b/arch/x86/include/asm/rdt_common.h
> @@ -0,0 +1,25 @@
> +#ifndef _X86_RDT_H_
> +#define _X86_RDT_H_
> +
> +#define MSR_IA32_PQR_ASSOC	0x0c8f
> +
> +/**
> + * struct intel_pqr_state - State cache for the PQR MSR
> + * @rmid:		The cached Resource Monitoring ID
> + * @closid:		The cached Class Of Service ID
> + * @rmid_usecnt:	The usage counter for rmid
> + *
> + * The upper 32 bits of MSR_IA32_PQR_ASSOC contain closid and the
> + * lower 10 bits rmid. The update to MSR_IA32_PQR_ASSOC always
> + * contains both parts, so we need to cache them.
> + *
> + * The cache also helps to avoid pointless updates if the value does
> + * not change.
> + */
> +struct intel_pqr_state {
> +	u32			rmid;
> +	u32			closid;
> +	int			rmid_usecnt;
> +};
> +
> +#endif

So why not call this file PQR something or other? That's all there is.

> diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
> index 751bf4b..9149577 100644
> --- a/arch/x86/include/asm/switch_to.h
> +++ b/arch/x86/include/asm/switch_to.h
> @@ -8,6 +8,9 @@ struct tss_struct;
>  void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
>  		      struct tss_struct *tss);
>  
> +#include <asm/intel_rdt.h>
> +#define finish_arch_switch(prev)	intel_rdt_sched_in()

Right, so please stuff that in __switch_to(), I think I can kill
finish_arch_switch() entirely.

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