linux-kernel - Re: [PATCH 4/7] x86/intel_rdt: Implement scheduling support for Intel RDT

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Date:	Fri, 15 May 2015 21:39:05 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>
cc:	vikas.shivappa@...el.com, x86@...nel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	tj@...nel.org, peterz@...radead.org, matt.fleming@...el.com,
	will.auld@...el.com, peter.zijlstra@...el.com,
	h.peter.anvin@...el.com, kanaka.d.juvva@...el.com,
	mtosatti@...hat.com
Subject: Re: [PATCH 4/7] x86/intel_rdt: Implement scheduling support for
 Intel RDT

On Mon, 11 May 2015, Vikas Shivappa wrote:
>  struct rdt_subsys_info {
>  	/* Clos Bitmap to keep track of available CLOSids.*/
> @@ -24,6 +30,11 @@ struct clos_cbm_map {
>  	unsigned int clos_refcnt;
>  };
>  
> +static inline bool rdt_enabled(void)
> +{
> +	return static_key_false(&rdt_enable_key);

So again, why this useless helper function for a single call site?

> +static inline void intel_rdt_sched_in(void)
> +{
> +	if (rdt_enabled())
> +		__rdt_sched_in();
> +}
  
> +void __rdt_sched_in(void)
> +{
> +	struct task_struct *task = current;
> +	struct intel_rdt *ir;
> +	unsigned int clos;
> +
> +	/*
> +	 * This needs to be fixed
> +	 * to cache the whole PQR instead of just CLOSid.
> +	 * PQR has closid in high 32 bits and CQM-RMID in low 10 bits.
> +	 * Should not write a 0 to the low 10 bits of PQR
> +	 * and corrupt RMID.

And why is this not fixed __BEFORE__ this patch? You can do the
changes to struct intel_cqm_state in a seperate patch and then do the
proper implementation from the beginning instead of providing a half
broken variant which gets replaced in the next patch.

Thanks,

	tglx
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