linux-kernel - Re: resctrl2

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Date:   Tue, 19 Sep 2023 14:53:07 +0200
From:   Peter Newman <peternewman@...gle.com>
To:     Tony Luck <tony.luck@...el.com>
Cc:     Reinette Chatre <reinette.chatre@...el.com>,
        "james.morse@....com" <james.morse@....com>,
        Babu Moger <babu.moger@....com>,
        Amit Singh Tomar <amitsinght@...vell.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        George Cherian <gcherian@...vell.com>,
        "robh@...nel.org" <robh@...nel.org>,
        Drew Fustini <dfustini@...libre.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: resctrl2 - status

Hi Tony,

On Wed, Sep 6, 2023 at 8:21 PM Tony Luck <tony.luck@...el.com> wrote:
> I've just pushed an updated set of patches to:
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux.git resctrl_v65

I'm trying to understand the purpose of the resctrl_resource struct
defined here:

https://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux.git/tree/include/linux/resctrl.h?h=resctrl2_v65#n356

>From the common fields, it seems to be something with a name and some
info files that can be divided into domains and should be told when
CPUs are hotplugged. (I skipped the scope field because I couldn't
find any references outside fs/resctrl2/arch). The remaining fields
are explicitly disjoint depending on whether we're talking about
monitoring or allocation.

>From this I don't get a strong sense that a "resource" is really a
thing and I think James's resctrl_schema struct only for the purpose
of resource allocation was more the right direction for common code.
Outwardly, resctrl groups seem to be the only thing relating
monitoring to allocation.

Is there a good reason for the common code to understand relationships
between monitors and schemas with the same name? If not, I think it
would make more sense to register monitors and control schemata
independently.

-Peter