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

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Message-ID: <78c88c6d-2e8d-42d1-a6f2-1c5ac38fb258@intel.com>
Date: Thu, 1 Feb 2024 10:46:45 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>, "Peter
 Newman" <peternewman@...gle.com>, Jonathan Corbet <corbet@....net>, "Shuah
 Khan" <skhan@...uxfoundation.org>, <x86@...nel.org>
CC: Shaopeng Tan <tan.shaopeng@...itsu.com>, James Morse
	<james.morse@....com>, Jamie Iles <quic_jiles@...cinc.com>, Babu Moger
	<babu.moger@....com>, Randy Dunlap <rdunlap@...radead.org>, Drew Fustini
	<dfustini@...libre.com>, <linux-kernel@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <patches@...ts.linux.dev>
Subject: Re: [PATCH v15-RFC 0/8] Add support for Sub-NUMA cluster (SNC)
 systems

Hi Tony,

On 1/30/2024 2:20 PM, Tony Luck wrote:
> This is the re-worked version of this series that I promised to post
> yesterday. Check that e-mail for the arguments for this alternate
> approach.
> 
> https://lore.kernel.org/all/ZbhLRDvZrxBZDv2j@agluck-desk3/
> 
> Apologies to Drew Fustini who I'd somehow dropped from later versions
> of this series. Drew: you had made a comment at one point that having
> different scopes within a single resource may be useful on RISC-V.
> Version 14 included that, but it's gone here. Maybe multiple resctrl
> "struct resource" for a single h/w entity like L3 as I'm doing in this
> version could work for you too?
> 
> Patches 1-5 are almost completely rewritten based around the new
> idea to give CMT and MBM their own "resource" instead of sharing
> one with L3 CAT. This removes the need for separate domain lists,
> and thus most of the churn of the previous version of this series.

I do not see it as removing the need for separate domain lists but
instead keeping the idea of separate domain lists but in this case
duplicating the resource in order to host the second domain
list. This solution also keeps the same structures for control and
monitoring that previous version cleaned up [1].
To me this thus seems like a similar solution as v14 but with
additional duplication due to an extra resource and without the cleanup.

Reinette

[1] https://lore.kernel.org/lkml/20240126223837.21835-5-tony.luck@intel.com/