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

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Date:   Mon, 13 Jan 2020 12:08:47 +0000
From:   "Zengtao (B)" <prime.zeng@...ilicon.com>
To:     Valentin Schneider <valentin.schneider@....com>,
        Morten Rasmussen <morten.rasmussen@....com>
CC:     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

> -----Original Message-----
> From: Valentin Schneider [mailto:valentin.schneider@....com]
> Sent: Monday, January 13, 2020 7:17 PM
> To: Zengtao (B); Morten Rasmussen
> Cc: Sudeep Holla; Linuxarm; Greg Kroah-Hartman; Rafael J. Wysocki;
> linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] cpu-topology: warn if NUMA configurations
> conflicts with lower layer
> 
> On 13/01/2020 06:51, Zengtao (B) wrote:
> > I have tried both, this previous one don't work. But this one seems
> work
> > correctly with the warning message printout as expected.
> >
> 
> Thanks for trying it out.
> 
> > This patch is based on the fact " non-NUMA spans shouldn't overlap ",
> I am
> > not quite sure if this is always true?
> >
> 
> I think this is required for get_group() to work properly. Otherwise,
> successive get_group() calls may override (and break) the sd->groups
> linking as you initially reported.
> 
> In your example, for MC level we have
> 
>   tl->mask(3) == 3-7
>   tl->mask(4) == 4-7
> 
> Which partially overlaps, causing the relinking of '7->3' to '7->4'. Valid
> configurations would be
> 
>   wholly disjoint:
>   tl->mask(3) == 0-3
>   tl->maks(4) == 4-7
> 
>   equal:
>   tl->mask(3) == 3-7
>   tl->mask(4) == 3-7
> 
> > Anyway, Could you help to raise the new patch?
> >
> 
> Ideally I'd like to be able to reproduce this locally first (TBH I'd like
> to get my first suggestion to work since it's less intrusive). Could you
> share how you were able to trigger this? Dietmar's been trying to
> reproduce
> this with qemu but I don't think he's there just yet.

Do you have got a hardware platform with clusters?what's the hardware
Cpu topology?

Regards
Zengtao