linux-kernel - Re: [PATCH v3 04/10] x86/resctrl: Detect and configure Slow Memory Bandwidth allocation

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Date:   Tue, 23 Aug 2022 15:47:34 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Babu Moger <babu.moger@....com>, <fenghua.yu@...el.com>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <eranian@...gle.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <corbet@....net>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <bagasdotme@...il.com>
Subject: Re: [PATCH v3 04/10] x86/resctrl: Detect and configure Slow Memory
 Bandwidth allocation

Hi Babu,

On 8/22/2022 6:43 AM, Babu Moger wrote:
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 6c38427b71a2..36ad97ab7342 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -253,6 +253,37 @@ static bool __rdt_get_mem_config_amd(struct rdt_resource *r)
>  	return true;
>  }
>  
> +static bool __rdt_get_s_mem_config_amd(struct rdt_resource *r)
> +{
> +	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> +	union cpuid_0x10_3_eax eax;
> +	union cpuid_0x10_x_edx edx;
> +	u32 ebx, ecx;
> +
> +	cpuid_count(0x80000020, 2, &eax.full, &ebx, &ecx, &edx.full);
> +	hw_res->num_closid = edx.split.cos_max + 1;
> +	r->default_ctrl = MAX_MBA_BW_AMD;
> +
> +	/* AMD does not use delay */
> +	r->membw.delay_linear = false;
> +	r->membw.arch_needs_linear = false;
> +
> +	/*
> +	 * AMD does not use memory delay throttle model to control
> +	 * the allocation like Intel does.
> +	 */
> +	r->membw.throttle_mode = THREAD_THROTTLE_UNDEFINED;
> +	r->membw.min_bw = 0;
> +	r->membw.bw_gran = 1;
> +	/* Max value is 2048, Data width should be 4 in decimal */
> +	r->data_width = 4;
> +
> +	r->alloc_capable = true;
> +	r->alloc_enabled = true;
> +
> +	return true;
> +}
> +


>From what I can tell this new function is almost identical to (it differs with
one character from) __rdt_get_mem_config_amd(). Could it be refactored to
avoid such duplication?

Reinette