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

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Message-ID: <d5d040db-0052-7054-f55a-5928360d536d@amd.com>
Date:   Wed, 24 Aug 2022 11:48:13 -0500
From:   "Moger, Babu" <babu.moger@....com>
To:     Reinette Chatre <reinette.chatre@...el.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 Reinette,

On 8/23/22 17:47, Reinette Chatre wrote:
> 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?

Yes. Sure. We can do that.

Thanks