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

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Date:   Tue, 30 Apr 2019 02:50:58 -0400
From:   Len Brown <lenb@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     X86 ML <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 2:05 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Tue, Feb 26, 2019 at 01:19:58AM -0500, Len Brown wrote:
> >  Documentation/cputopology.txt                | 72 ++++++++++++++---------
> >  Documentation/x86/topology.txt               |  6 +-
> >  arch/x86/include/asm/processor.h             |  5 +-
> >  arch/x86/include/asm/smp.h                   |  1 +
> >  arch/x86/include/asm/topology.h              |  5 ++
> >  arch/x86/kernel/cpu/topology.c               | 85 +++++++++++++++++++++-------
> >  arch/x86/kernel/smpboot.c                    | 73 +++++++++++++++++++++++-
> >  arch/x86/xen/smp_pv.c                        |  1 +
> >  drivers/base/topology.c                      | 22 +++++++
> >  drivers/hwmon/coretemp.c                     |  9 +--
> >  drivers/powercap/intel_rapl.c                | 75 +++++++++++++-----------
> >  drivers/thermal/intel/x86_pkg_temp_thermal.c |  9 +--
> >  include/linux/topology.h                     |  6 ++
> >  13 files changed, 276 insertions(+), 93 deletions(-)
>
> Should we not also have changes to
> arch/x86/kernel/cpu/proc.c:show_cpuinfo_cores() ?

Good question.
I was thinking that /proc/cpuinfo was sort of the legacy API, and
adding a field might break something.
While adding an attribute to sysfs topology directory was the
compatible/safe way to make additions.

/proc/cpuinfo has these fields today:

physical id : 0
    this is the physical package id
siblings : 8
    this is the count of cpus in the same package
core id : 3
    this is cpu_core_id
cpu cores : 4
    this is booted_cores

If one were to make a change here, I'd consider adding the (physical) die_id,
though it is already in sysfs topology as an attribute.

Not sure if it would then make sense to print the count of cpus in the die.
Not sure what I'd name it, and this info is already in sysfs as a map and list.


Len Brown, Intel Open Source Technology Center