linux-kernel - RE: [PATCH v20 00/18] Add support for Sub-NUMA cluster (SNC) systems

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Message-ID: <SJ1PR11MB60833EDA722D482EDF52C7EEFCC12@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date: Thu, 13 Jun 2024 21:02:54 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: "Chatre, Reinette" <reinette.chatre@...el.com>, "babu.moger@....com"
	<babu.moger@....com>, "Yu, Fenghua" <fenghua.yu@...el.com>, "Wieczor-Retman,
 Maciej" <maciej.wieczor-retman@...el.com>, Peter Newman
	<peternewman@...gle.com>, James Morse <james.morse@....com>, Drew Fustini
	<dfustini@...libre.com>, Dave Martin <Dave.Martin@....com>
CC: "x86@...nel.org" <x86@...nel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "patches@...ts.linux.dev"
	<patches@...ts.linux.dev>
Subject: RE: [PATCH v20 00/18] Add support for Sub-NUMA cluster (SNC) systems

> Looking at the series again, I see this approach adds lots of code.
> Look at this structure.
> 
> 
> @@ -187,10 +196,12 @@ struct rdt_resource {
>   	bool			alloc_capable;
>   	bool			mon_capable;
>   	int			num_rmid;
> -	enum resctrl_scope	scope;
> +	enum resctrl_scope	ctrl_scope;
> +	enum resctrl_scope	mon_scope;
>   	struct resctrl_cache	cache;
>   	struct resctrl_membw	membw;
> -	struct list_head	domains;
> +	struct list_head	ctrl_domains;
> +	struct list_head	mon_domains;
>   	char			*name;
>   	int			data_width;
>   	u32			default_ctrl;
> 
> There are two scope fields.
> There are two domains fields.

I might at some future time split struct rdt_resource into struct
rdt_ctrl_resource and struct rdt_mon_resource.  That would get rid of
multiple scope and domain fields. There are also a bunch of fields that
are specific to just ctrl or mon functions.

That would require other churn. E.g. getting rid of the
rdt_resources_all[] array and the macros that scan it to perform
various actions. Replace with two lists, one each for active ctrl/mon
resources. Once James' patches to split into architecture vs. generic
parts are applied this might be useful so that CPU vendors could add
resources that didn't have equivalents for other architectures.

There isn't a pressing need for that today. But splitting the rdt_domain
structure now makes for a good base to build on later (if needed).

-Tony