linux-kernel - RE: [PATCH v3] x86,sched: allow topologies where NUMA nodes share an LLC

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F7B3BAF7B@ORSMSX110.amr.corp.intel.com>
Date:   Thu, 29 Mar 2018 16:29:10 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        "Schofield, Alison" <alison.schofield@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        David Rientjes <rientjes@...gle.com>,
        "Igor Mammedov" <imammedo@...hat.com>,
        Prarit Bhargava <prarit@...hat.com>,
        "brice.goglin@...il.com" <brice.goglin@...il.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3] x86,sched: allow topologies where NUMA nodes share
 an LLC

> Hmm, if we shrink llc-size by splitting it, do we also need to create a
> unique "id" for each slice?

RDT uses the cache id ... but it doesn't play well with cluster on die mode ... so our
recommendation is to not use RDT if COD mode is enabled.

If the result of these changes happens to be some easy way for RDT to tell that
COD mode is on, we'll add a check to the init/mount code to enforce not using
them together.

-Tony