From: Brice Goglin <Brice.Goglin@inria.fr>
To: James Morse <james.morse@arm.com>
Cc: Jeremy Linton <Jeremy.Linton@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: offline CPUs shown in sysfs core_siblings mask
Date: Thu, 12 Sep 2019 10:09:19 +0200 [thread overview]
Message-ID: <c635c893-6ed4-c21b-6bb9-b1690b191a95@inria.fr> (raw)
In-Reply-To: <4568af7d-724e-5ee7-3ba1-87a5db662447@arm.com>
Le 11/09/2019 à 18:06, James Morse a écrit :
> On 9/11/19 2:23 PM, Brice Goglin wrote:
>> We have a report from a user of hwloc/lstopo on ThunderX2 that complains
>> that offline CPUs are shown in sysfs cpu core_siblings files.
>
> Hmmm, this doesn't happen on my TX2, running mainline:
> root@eglon:/sys/devices/system/cpu# cat cpu1/topology/core_siblings
> 00000000,00000000,00000000,00000000,ffffffff,ffffffff,ffffffff,ffffffff
> root@eglon:/sys/devices/system/cpu# echo 0 > cpu0/online
> root@eglon:/sys/devices/system/cpu# cat cpu1/topology/core_siblings
> 00000000,00000000,00000000,00000000,ffffffff,ffffffff,ffffffff,fffffffe
> root@eglon:/sys/devices/system/cpu# echo 1 > cpu0/online
> root@eglon:/sys/devices/system/cpu# cat cpu1/topology/core_siblings
> 00000000,00000000,00000000,00000000,ffffffff,ffffffff,ffffffff,ffffffff
>
>
>> Only 8 online logicial CPUs, but 56 are shown in these masks. This is on
>> RHEL7 with a kernel 4.14.0-115.2.2.el7a.aarch64 but I couldn't find any
>> significant change in Linux git.
>
> Could you try a recent mainline kernel?
>
> Does your system have an ACPI PPTT table? (I assume its ACPI)
>
> Prior to the ACPI PPTT table handling, it wasn't possible for an arm64
> ACPI system to know about packages and threads.
>
Yes the machine has an ACPI PPTT table. I am working with admins to
verify that recent kernels with 7f9545aa1a91 work better.
Thanks
Brice
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prev parent reply other threads:[~2019-09-12 8:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 13:23 offline CPUs shown in sysfs core_siblings mask Brice Goglin
2019-09-11 16:06 ` James Morse
2019-09-11 16:14 ` Sudeep Holla
2019-09-12 8:09 ` Brice Goglin [this message]
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