linux-kernel - Re: [PATCH v2 3/3] x86/resctrl: Add "*" shorthand to set minimum io

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Message-ID: <js2hrscjtioxvfe2la3ycf43cuj536smsj4voecl5ps3xpit2j@qi4rh5mgttpd>
Date: Thu, 25 Dec 2025 17:50:19 -0500
From: Aaron Tomlin <atomlin@...mlin.com>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: Reinette Chatre <reinette.chatre@...el.com>, 
	"Moger, Babu" <bmoger@....com>, "Dave.Martin@....com" <Dave.Martin@....com>, 
	"james.morse@....com" <james.morse@....com>, "babu.moger@....com" <babu.moger@....com>, 
	"tglx@...utronix.de" <tglx@...utronix.de>, "mingo@...hat.com" <mingo@...hat.com>, 
	"bp@...en8.de" <bp@...en8.de>, "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>, 
	"sean@...e.io" <sean@...e.io>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] x86/resctrl: Add "*" shorthand to set minimum
 io_alloc CBM for all domains

On Fri, Dec 19, 2025 at 03:05:34PM -0800, Luck, Tony wrote:
> I still don't see a good reason for the kernel to handle any of this.
> 
> Having some resctrl control files accept wildcards while others don't
> seems like a confusing interface. Is there something I'm missing that
> makes io_alloc harder for users to handle than L3 or MB in schemata?
> 
> Babu's simpler implementation for io_alloc makes me more comfortable
> with this. But I'm still unconvinced that wildcards must be handled
> in kernel code.

Hi Tony,

I appreciate your reservations regarding where the responsibility for such
abstractions should lie. However, I am of the view that forcing the user to
manually specify every domain for a global policy represents an unnecessary
hurdle that the kernel is uniquely positioned to clear.

I shall indeed employ Babu's suggestion in a follow-up patch for review, as
the resulting simplicity of the implementation should, I hope, alleviate
any concerns regarding the addition of technical debt.


Kind regards,
-- 
Aaron Tomlin

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