linux-kernel - Re: [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer

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Message-ID: <ac3ec325-bbae-aeaf-0072-b91445bf54bc@arm.com>
Date:   Thu, 9 Jan 2020 13:07:58 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Morten Rasmussen <morten.rasmussen@....com>
Cc:     "Zengtao (B)" <prime.zeng@...ilicon.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Linuxarm <linuxarm@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpu-topology: warn if NUMA configurations conflicts with
 lower layer

On 09/01/2020 12:05, Morten Rasmussen wrote:
> On Mon, Jan 06, 2020 at 03:31:24PM +0100, Dietmar Eggemann wrote:
>> Your issue is related to the 'numa mask check for scheduler MC
>> selection' functionality.  It was introduced by commit 37c3ec2d810f and
>> re-introduced by commit e67ecf647020 later. I don't know why we need
>> this functionality?
> 
> That functionality is to ensure that we don't break the sched_domain
> hierarchy for numa-in-cluster systems. We have to be sure that the MC
> domain is always smaller or equal to the NUMA node span.

Thanks! And we already have Arm64 systems today using 'numa-in-cluster',
as I learned yesterday.