linux-kernel - Re: [PATCH v4 23/31] x86,fs/resctrl: Handle domain creation/deletion for RDT_RESOURCE_PERF

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Message-ID: <24db7e9c-55f7-44c0-b32e-342a7dc29ce3@intel.com>
Date: Thu, 8 May 2025 08:58:22 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghuay@...dia.com>, "Maciej
 Wieczor-Retman" <maciej.wieczor-retman@...el.com>, Peter Newman
	<peternewman@...gle.com>, James Morse <james.morse@....com>, Babu Moger
	<babu.moger@....com>, Drew Fustini <dfustini@...libre.com>, Dave Martin
	<Dave.Martin@....com>, Anil Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	Chen Yu <yu.c.chen@...el.com>
CC: <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v4 23/31] x86,fs/resctrl: Handle domain creation/deletion
 for RDT_RESOURCE_PERF_PKG

Hi Tony,

On 4/28/25 5:33 PM, Tony Luck wrote:
> The L3 resource has several requirements for domains. There are structures
> that hold the 64-bit values of counters, and elements to keep track of
> the overflow and limbo threads.
> 
> None of these are needed for the PERF_PKG resource. The hardware counters
> are wide enough that they do not wrap around for decades.
> 
> Define a new rdt_perf_pkg_mon_domain structure which just consists of
> the standard rdt_domain_hdr to keep track of domain id and CPU mask.
> 
> Change domain_add_cpu_mon(), domain_remove_cpu_mon(),
> resctrl_offline_mon_domain(), and resctrl_online_mon_domain() to check
> resource type and perform only the operations needed for domsins in the

domsins -> domains

> PERF_PKG resource.
> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---
>  arch/x86/kernel/cpu/resctrl/core.c | 41 ++++++++++++++++++++++++++++++
>  fs/resctrl/rdtgroup.c              |  4 +++
>  2 files changed, 45 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 0103f577e4ca..97fb2001c8d8 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -543,6 +543,38 @@ static void setup_l3_mon_domain(int cpu, int id, struct rdt_resource *r, struct
>  	}
>  }
>  
> +/**
> + * struct rdt_perf_pkg_mon_domain - CPUs sharing an Intel-PMT-scoped resctrl monitor resource

This should not be architecture specific. My first reaction was that this belongs in fs code
but I remember that the advice is that things should only move there when needed to be
shared among architectures. This may thus be ok like this for now.

Reinette