linux-kernel - Re: [PATCH v15-RFC 0/8] Add support for Sub-NUMA cluster (SNC) systems

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Date: Mon, 12 Feb 2024 13:43:56 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>, "babu.moger@....com"
	<babu.moger@....com>, "Yu, Fenghua" <fenghua.yu@...el.com>, Peter Newman
	<peternewman@...gle.com>, Jonathan Corbet <corbet@....net>, Shuah Khan
	<skhan@...uxfoundation.org>, "x86@...nel.org" <x86@...nel.org>
CC: Shaopeng Tan <tan.shaopeng@...itsu.com>, James Morse
	<james.morse@....com>, Jamie Iles <quic_jiles@...cinc.com>, Randy Dunlap
	<rdunlap@...radead.org>, Drew Fustini <dfustini@...libre.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH v15-RFC 0/8] Add support for Sub-NUMA cluster (SNC)
 systems

Hi Tony,

On 2/12/2024 11:57 AM, Luck, Tony wrote:
>>> To be honest, I like this series more than the previous series. I always
>>> thought RDT_RESOURCE_L3_MON should have been a separate resource by itself.
>>
>> Would you prefer that your "Reviewed-by" tag be removed from the
>> previous series?
> 
> I'm thinking that I could continue splitting things and break "struct rdt_resource" into
> separate "ctrl" and "mon" structures. Then we'd have a clean split from top to bottom.

It is not obvious what you mean with "continue splitting things". Are you
speaking about "continue splitting from v14" or "continue splitting from v15-RFC"?

I think that any solution needs to consider what makes sense for resctrl
as a whole instead of how to support SNC with smallest patch possible.

There should not be any changes that makes resctrl harder to understand
and maintain, as exemplified by confusion introduced by a simple thing as
resource name choice [1].

> 
> Doing that would get rid of the rdt_resources_all[] array. Replacing with individual
> rdt_hw_ctrl_resource and rdt_hw_mon_resource declarations for each feature.
>
> Features found on a system would be added to a list of ctrl or list of mon resources.

Could you please elaborate what is architecturally wrong with v14 and how this
new proposal addresses that?

Reinette

[1] https://lore.kernel.org/lkml/ZcZyqs5hnQqZ5ZV0@agluck-desk3/