linux-kernel - RE: [PATCH v3 3/8] x86/resctrl: Add a new node-scoped resource to rdt_resources

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Message-ID: <SJ1PR11MB6083E1B292969DA2AE1FC67DFC3EA@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Thu, 20 Jul 2023 21:56:50 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "Chatre, Reinette" <reinette.chatre@...el.com>
CC:     "Yu, Fenghua" <fenghua.yu@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <skhan@...uxfoundation.org>,
        "x86@...nel.org" <x86@...nel.org>,
        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>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: RE: [PATCH v3 3/8] x86/resctrl: Add a new node-scoped resource to
 rdt_resources_all[]

> To deal with these complexities I would like to consider if it may
> make things simpler to always (irrespective of allocation and
> monitoring scope) maintain allocation and monitoring domain lists.
> Each list need only carry data appropriate to its use ... the allocation
> list only has data relevant to allocation, the monitoring list only
> has data relevant to monitoring. This is the struct rdt_domain related
> split I mentioned previously.
>
> Code could become something like:

resctrl_online_cpu()
{
	...
	for_each_alloc_capable_rdt_resource(r)
		alloc_domain_add_cpu(...)
	for_each_mon_capable_rdt_resource(r)
		mon_domain_add_cpu(...)
	...
}

> This would reduce complication in domain_add_cpu() since each domain list
> only need to concern itself with monitoring or allocation.

This does seem a worthy target.

I started on a patch to so this ... but I'm not sure I have the stamina or the time
to see it through. 

I split struct rdt_domain into rdt_ctrl_domain and rdt_mon_domain. But that
led to also splitting the rdt_hw_domain structure into two, and then splitting
the resctrl_to_arch_dom() function, and then another and another.

That process will eventually converge (there are a finite number of lines
of code) .... but it will be a big patch. I don't see how to stage it a piece
at a time.

-Tony