linux-kernel - Re: [PATCH 0/14] v2 multi-die/package topology support

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Date:   Thu, 7 Mar 2019 14:59:25 +0000
From:   Morten Rasmussen <morten.rasmussen@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Len Brown <lenb@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/14] v2 multi-die/package topology support

On Tue, Feb 26, 2019 at 07:53:58PM +0100, Peter Zijlstra wrote:
> On Tue, Feb 26, 2019 at 01:19:58AM -0500, Len Brown wrote:
> > Added sysfs package_threads, package_threads_list
> > 
> > 	Added this attribute to show threads siblings in a package.
> > 	Exactly same as "core_siblings above", a name now deprecated.
> > 	This attribute name and definition is immune to future
> > 	topology changes.
> > 
> > 	Suggested by Brice.
> > 
> > Added sysfs die_threads, die_threads_list
> > 
> > 	Added this attribute to show which threads siblings in a die.
> > 	V1 had proposed putting this info into "core_siblings", but we
> > 	decided to leave that legacy attribute alone.
> > 	This attribute name and definition is immune to future
> > 	topology changes.
> > 
> > 	On a single die-package system this attribute has same contents
> > 	as "package_threads".
> > 
> > 	Suggested by Brice.
> > 
> > Added sysfs core_threads, core_threads_list
> > 
> > 	Added this attribute to show which threads siblings in a core.
> > 	Exactly same as "thread_siblings", a name now deprecated.
> > 	This attribute name and definition is immune to future
> > 	topology changes.
> > 
> > 	Suggested by Brice.
> 
> I think I prefer 's/threads/cpus/g' on that. Threads makes me think SMT,
> and I don't think there's any guarantee the part in question will have
> SMT on.

I think 'threads' is a bit confusing as well. We seem to be using 'cpu'
everywhere for something we can schedule tasks on, including the sysfs
/sys/devices/system/cpu/ subdirs for each SMT thread on SMT systems.

Another thing that I find confusing is that with this series we a new
die id/mask which is totally unrelated to the DIE level in the
sched_domain hierarchy. We should rename DIE level to something that
reflects what it really is. If we can agree on that ;-)

NODE level?

Morten