linux-kernel - RE: RE: [PATCH v8 08/21] x86/resctrl: Expand the width of dom_id by replacing mon_data

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Message-ID: <DS7PR11MB607779FA7437306CEB8D08BCFCBB2@DS7PR11MB6077.namprd11.prod.outlook.com>
Date: Tue, 22 Apr 2025 18:10:27 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: "Moger, Babu" <bmoger@....com>, James Morse <james.morse@....com>,
	"x86@...nel.org" <x86@...nel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: "Chatre, Reinette" <reinette.chatre@...el.com>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
	<bp@...en8.de>, H Peter Anvin <hpa@...or.com>, Babu Moger
	<Babu.Moger@....com>, "shameerali.kolothum.thodi@...wei.com"
	<shameerali.kolothum.thodi@...wei.com>, D Scott Phillips OS
	<scott@...amperecomputing.com>, "carl@...amperecomputing.com"
	<carl@...amperecomputing.com>, "lcherian@...vell.com" <lcherian@...vell.com>,
	"bobo.shaobowang@...wei.com" <bobo.shaobowang@...wei.com>,
	"tan.shaopeng@...itsu.com" <tan.shaopeng@...itsu.com>,
	"baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>, Jamie Iles
	<quic_jiles@...cinc.com>, Xin Hao <xhao@...ux.alibaba.com>,
	"peternewman@...gle.com" <peternewman@...gle.com>, "dfustini@...libre.com"
	<dfustini@...libre.com>, "amitsinght@...vell.com" <amitsinght@...vell.com>,
	David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>, Dave
 Martin <dave.martin@....com>, "Ko, Koba" <kobak@...dia.com>, "Shanker
 Donthineni" <sdonthineni@...dia.com>, "fenghuay@...dia.com"
	<fenghuay@...dia.com>
Subject: RE: RE: [PATCH v8 08/21] x86/resctrl: Expand the width of dom_id by
 replacing mon_data_bits

>> kernfs lookups while creating new groups to find the matching one
>> and linking to the same ->priv pointer.
>> 
>
> oh ok.
>
> I went back and looked at the history.
> https://lore.kernel.org/all/20250228195913.24895-38-james.morse@arm.com/
>
> So you are saying, kernfs lookup method is much more complex. So, having 
> the global list is easy to traverse and efficient?

Complexity in the code to construct the path and do kernfs lookups to walk
that path (since kernfs doesn't provide a routine to do the path walk, just
individual directory lookups). There was some doubt whether James' code
got things right for the SNC case which has an extra sub-level of directories.

The latest version is far simpler to review and decide it is doing the right
thing in all configurations.

-Tony