From: Shrikanth Hegde <sshegde@linux.ibm.com>
To: Thomas Gleixner <tglx@linutronix.de>,
"Nysal Jan K.A." <nysal@linux.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.ibm.com>,
Laurent Dufour <ldufour@linux.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Nicholas Piggin <npiggin@gmail.com>,
"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
Michal Suchanek <msuchanek@suse.de>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 0/2] Skip offline cores when enabling SMT on PowerPC
Date: Mon, 1 Jul 2024 10:24:49 +0530 [thread overview]
Message-ID: <dcab2925-11cb-454a-ba1e-a32e06117ca4@linux.ibm.com> (raw)
In-Reply-To: <87sex26nlw.ffs@tglx>
On 6/25/24 2:54 AM, Thomas Gleixner wrote:
> On Tue, Jun 25 2024 at 00:41, Shrikanth Hegde wrote:
>> On 6/24/24 1:44 AM, Thomas Gleixner wrote:
>>> Right. So changing it not to online a thread when the full core is
>>> offline should not really break stuff.
>>>
>>> OTH, the mechanism to figure that out on x86 is definitely different and
>>> more complicated than on power because the sibling threads are not
>>> having consecutive CPU numbers.
>>
>> wouldn't topology_sibling_cpumask have this info?
>> If the mask is empty does it mean the core is offline?
>
> The mask is not yet available for the to be brought up CPU. That's
> established when the CPU boots. It might work because all threads are
> brought up during early boot for !~*&^!@% reasons, but then it won't
> work under all circumstances, e.g. 'maxcpus=$N'.
>
> We could fix that now with the new topology enumeration code, but that's
> a larger scale project.
Ok.
Can we please document the behavior on different platforms i.e on x86 and PowerPC?
May be in ABI/testing/sysfs-devices-system-cpu?
prev parent reply other threads:[~2024-07-01 4:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-12 18:50 [PATCH 0/2] Skip offline cores when enabling SMT on PowerPC Nysal Jan K.A.
2024-06-12 18:50 ` [PATCH 1/2] cpu/SMT: Enable SMT only if a core is online Nysal Jan K.A.
2024-06-12 18:50 ` [PATCH 2/2] powerpc/topology: Check " Nysal Jan K.A.
2024-06-24 19:06 ` Shrikanth Hegde
2024-06-25 6:13 ` Nysal Jan K.A.
2024-06-13 11:34 ` [PATCH 0/2] Skip offline cores when enabling SMT on PowerPC Michael Ellerman
2024-06-13 12:07 ` Michal Suchánek
2024-06-14 3:52 ` Nysal Jan K.A.
2024-06-23 20:14 ` Thomas Gleixner
2024-06-24 19:11 ` Shrikanth Hegde
2024-06-24 21:24 ` Thomas Gleixner
2024-07-01 4:54 ` Shrikanth Hegde [this message]
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