linux-kernel - Re: [PATCH v5 4/8] x86/resctrl: Add node-scope to the options for feature scope

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Message-ID: <ZRW69o0tNo2s8m+H@agluck-desk3>
Date:   Thu, 28 Sep 2023 10:42:14 -0700
From:   Tony Luck <tony.luck@...el.com>
To:     Reinette Chatre <reinette.chatre@...el.com>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <skhan@...uxfoundation.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-doc@...r.kernel.org,
        patches@...ts.linux.dev
Subject: Re: [PATCH v5 4/8] x86/resctrl: Add node-scope to the options for
 feature scope

On Mon, Sep 25, 2023 at 04:25:54PM -0700, Reinette Chatre wrote:
> Hi Tony,
> 
> On 8/29/2023 4:44 PM, Tony Luck wrote:
> > Currently supported resctrl features are all domain scoped the same as the
> > scope of the L2 or L3 caches.
> 
> fyi ... this patch series seems to use the terms "resctrl feature"
> and "resctrl resource" interchangeably and it is not always clear
> if the terms mean something different.

I think a "resctrl feature" is a h/w control or monitor feature. A
"resctrl resource" is "struct rdt_resource" (which may have more than
one "resctrl feature" attached to it. E.g. the RDT_RESOURCE_L3 resource
has L3 CAT, MBM, CQM attached).

> 
> > 
> > Add "node" as a new option for domain scope.
> 
> Could the commit message please get a snippet about what "node"
> represents and why this new scope is needed?

Yes. I've added a note.

> 
> > Signed-off-by: Tony Luck <tony.luck@...el.com>
> > ---
> >  include/linux/resctrl.h            | 1 +
> >  arch/x86/kernel/cpu/resctrl/core.c | 2 ++
> >  2 files changed, 3 insertions(+)
> > 
> > diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> > index 08382548571e..f55cf7afd4eb 100644
> > --- a/include/linux/resctrl.h
> > +++ b/include/linux/resctrl.h
> > @@ -163,6 +163,7 @@ struct resctrl_schema;
> >  enum resctrl_scope {
> >  	RESCTRL_L3_CACHE,
> >  	RESCTRL_L2_CACHE,
> > +	RESCTRL_NODE,
> >  };
> >  
> >  /**
> > diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> > index 3e08aa04a7ff..9fcc264fac6c 100644
> > --- a/arch/x86/kernel/cpu/resctrl/core.c
> > +++ b/arch/x86/kernel/cpu/resctrl/core.c
> > @@ -514,6 +514,8 @@ static int get_domain_id_from_scope(int cpu, enum resctrl_scope scope)
> >  		return get_cpu_cacheinfo_id(cpu, 3);
> >  	case RESCTRL_L2_CACHE:
> >  		return get_cpu_cacheinfo_id(cpu, 2);
> > +	case RESCTRL_NODE:
> > +		return cpu_to_node(cpu);
> >  	default:
> >  		WARN_ON_ONCE(1);
> >  		break;
> 
> 
> Reinette