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Subject: Re: [PATCH v2 0/9]  Introduce SMT level and add PowerPC support
From:   Sachin Sant <sachinp@linux.ibm.com>
In-Reply-To: <87edluh6ce.fsf@mail.lhotse>
Date:   Thu, 29 Jun 2023 19:01:22 +0530
Cc:     Laurent Dufour <ldufour@linux.ibm.com>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        linux-arch@vger.kernel.org, dave.hansen@linux.intel.com,
        open list <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>, bp@alien8.de,
        npiggin@gmail.com, tglx@linutronix.de
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To:     Michael Ellerman <mpe@ellerman.id.au>
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>>=20
>> Without this option but changing SMT level during runtime using
>> ppc64_cpu =E2=80=94smt=3D<level>, the SMT level is not retained after
>> cpu core add.
>=20
> That's because ppc64_cpu is not using the sysfs SMT control file, it's
> just onlining/offlining threads manually.
>=20
> If you run:
> $ ppc64_cpu --smt=3D4=20
>=20
> And then also do:
>=20
> $ echo 4 > /sys/devices/system/cpu/smt/control
>=20
> It should work as expected?

Thanks Michael. Yes this works. The SMT level is preserved
after a core add.

- Sachin