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From: Morten Rasmussen <morten.rasmussen@arm.com>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: "Zengtao (B)" <prime.zeng@hisilicon.com>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Linuxarm <linuxarm@huawei.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer
Date: Mon, 13 Jan 2020 13:22:14 +0000	[thread overview]
Message-ID: <20200113132214.GD10914@e105550-lin.cambridge.arm.com> (raw)
In-Reply-To: <f973e77b-9c0a-6506-da97-f7a0ea1829fd@arm.com>

On Sun, Jan 12, 2020 at 01:22:02PM +0000, Valentin Schneider wrote:
> On 09/01/2020 10:52, Morten Rasmussen wrote:
> >> AFAIA what matters here is memory controllers, less so LLCs. Cores within
> >> a single die could have private LLCs and separate memory controllers, or
> >> shared LLC and separate memory controllers.
> > 
> > Don't confuse cache boundaries, packages and nodes :-)
> > 
> > core_siblings are cpus in the same package and doesn't say anything
> > about cache boundaries. It is not given that there is sched_domain that
> > matches the core_sibling span.
> > 
> > The MC sched_domain is supposed to match the LLC span which might
> > different for core_siblings. So the about example should be valid for a
> > NUMA-in-package system with one package containing two nodes.
> > 
> 
> Right, the point I was trying to make is that node boundaries can be pretty
> much anything, so nodes can span over LLCs, or LLCs can span over nodes,
> which is why we need checks such as the one in arch_topology() that lets us
> build up a usable domain hierarchy (which cares about LLCs, at least at some
> level).

Indeed. The topology masks can't always be used as is to define the
sched_domain hierarchy.

  reply	other threads:[~2020-01-13 13:22 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-23  8:16 [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer z00214469
2019-12-31 16:40 ` Sudeep Holla
2020-01-02  3:05   ` Zengtao (B)
2020-01-02 11:29     ` Sudeep Holla
2020-01-02 12:47       ` Zengtao (B)
2020-01-02 13:22         ` Valentin Schneider
2020-01-02 19:30           ` Dietmar Eggemann
2020-01-03  4:24           ` Zengtao (B)
2020-01-03 10:57             ` Valentin Schneider
2020-01-03 12:14               ` Valentin Schneider
2020-01-03 17:20                 ` Dietmar Eggemann
2020-01-06  1:48                   ` Zengtao (B)
2020-01-06 14:31                     ` Dietmar Eggemann
2020-01-08  2:19                       ` Zengtao (B)
2020-01-09 11:05                       ` Morten Rasmussen
2020-01-09 12:07                         ` Dietmar Eggemann
2020-01-06  1:52                 ` Zengtao (B)
2020-01-03 11:40             ` Sudeep Holla
2020-01-06  1:37               ` Zengtao (B)
2020-01-09 10:43                 ` Morten Rasmussen
2020-01-09 12:58                   ` Zengtao (B)
2020-01-11 20:56                     ` Valentin Schneider
2020-01-13  6:51                       ` Zengtao (B)
2020-01-13 11:16                         ` Valentin Schneider
2020-01-13 12:08                           ` Zengtao (B)
2020-01-13 12:22                             ` Dietmar Eggemann
2020-01-13 14:49                       ` Dietmar Eggemann
2020-01-13 15:15                         ` Valentin Schneider
2020-01-09 10:52           ` Morten Rasmussen
2020-01-12 13:22             ` Valentin Schneider
2020-01-13 13:22               ` Morten Rasmussen [this message]
2020-01-02 13:59         ` Sudeep Holla

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