linux-kernel - Re: [PATCH v4] x86,sched: allow topologies where NUMA nodes share an LLC

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Date:   Wed, 4 Apr 2018 10:38:48 -0700
From:   Alison Schofield <alison.schofield@...el.com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.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 v4] x86,sched: allow topologies where NUMA nodes share an
 LLC

On Wed, Apr 04, 2018 at 10:24:49AM -0700, Tim Chen wrote:
> On 04/03/2018 02:12 PM, Alison Schofield wrote:
> 
> > +
> > +	/*
> > +	 * topology_sane() considers LLCs that span NUMA nodes to be
> > +	 * insane and will display a warning message. Bypass the call
> > +	 * to topology_sane() for snc_cpu's to avoid that warning.
> > +	 */
> > +
> > +	if (!topology_same_node(c, o) && x86_match_cpu(snc_cpu)) {
> > +		/* Indicate that package has NUMA nodes inside: */
> > +		x86_has_numa_in_package = true;
> 
> Why does the x86_has_numa_in_package has to be set here when it would have
> been done later in set_cpu_sibling_map?

Tim,
I had that same thought when you commented on it previously. After 
discussing w DaveH, decided that match_llc() and match_die(c,0)
could be different and chose to be (cautiously) redundant.
alisons



> 
> > +
> > +		/*
> > +		 * false means 'c' does not share the LLC of 'o'.
> > +		 * Note: this decision gets reflected all the way
> > +		 * out to userspace.
> > +		 */
> > +
> > +		return false;
> 
> Thanks.
> 
> Tim