linux-kernel - Re: [PATCH v2] x86,sched: allow topologies where NUMA nodes share an LLC

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Message-ID: <20180326224546.yu5lkk7t22zxfikj@agluck-desk>
Date:   Mon, 26 Mar 2018 15:45:46 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Alison Schofield <alison.schofield@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Luck@...son-desk.jf.intel.com,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        David Rientjes <rientjes@...gle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Prarit Bhargava <prarit@...hat.com>, brice.goglin@...il.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86,sched: allow topologies where NUMA nodes share an
 LLC

On Mon, Mar 26, 2018 at 03:19:48PM -0700, Alison Schofield wrote:
> On Thu, Mar 22, 2018 at 04:30:29PM -0700, Luck, Tony wrote:
> > On Thu, Mar 22, 2018 at 01:49:22PM -0700, Alison Schofield wrote:
> > > +	if (!topology_same_node(c, o) &&
> > > +	    (c->x86_vendor == X86_VENDOR_INTEL &&
> > > +	     c->x86_model == INTEL_FAM6_SKYLAKE_X)) {
> > 
> > Maybe make life easier in the future to add more models
> > to the list by using x86_match_cpu() here?
> > 
> > -Tony
> 
> Tony - 
>  Am I on the right track below?
> 
> Define like this:
> static const __initconst struct x86_cpu_id snc_cpu[] = {
> 	{ X86_VENDOR_INTEL, 6, INTEL_FAM6_SKYLAKE_X },
> 	{}
> };
> 
> Use like this:
> if (!topology_same_node(c, o) && x86_match_cpu(snc_cpu)) {

Alison,

Exactly right.  You can decide how much of the comment
that was before the "if (!topology_same_node(c, o) ..."
can be moved to before the definition of snc_cpu[]. I'm
too lazy to go back to the original patch to read it, but
I suspect most/all of it would be better descibing the
data structure than cluttering up the code that uses it.

-Tony