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Message-ID: <20180407001701.GA18897@alison-desk.jf.intel.com> Date: Fri, 6 Apr 2018 17:17:01 -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 12:00:45PM -0700, Alison Schofield wrote: > On Wed, Apr 04, 2018 at 11:42:11AM -0700, Tim Chen wrote: > > On 04/04/2018 10:38 AM, Alison Schofield wrote: > > > 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 > > > > If it is redundant, I suggest it be removed, and only added if > > there is truly a case where the current logic > > > > if (match_die(c, o) && !topology_same_node(c, o)) > > x86_has_numa_in_package = true; > > > > fails. And also the modification of this logic should be at the > > same place for easy code maintenance. > > That makes good sense. I'll look to define the difference or remove > the redundancy. > > alisons I found not reason for the redundancy via experimentation w my Skylake, nor through code examination. I've removed it in v5. I'll see if anyone claims theoretical case. alisons > > > > > Tim > > > > > > > > > > > > > >> > > >>> + > > >>> + /* > > >>> + * 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 > >
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