linux-kernel - Re: [PATCH v2 0/9] Introduce SMT level and add PowerPC support

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Message-Id: <E68433D6-F103-4B58-A0DC-AD1099F8CC05@linux.ibm.com>
Date:   Thu, 29 Jun 2023 19:01:22 +0530
From:   Sachin Sant <sachinp@...ux.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Laurent Dufour <ldufour@...ux.ibm.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-arch@...r.kernel.org, dave.hansen@...ux.intel.com,
        open list <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, bp@...en8.de,
        npiggin@...il.com, tglx@...utronix.de
Subject: Re: [PATCH v2 0/9]  Introduce SMT level and add PowerPC support


>> 
>> Without this option but changing SMT level during runtime using
>> ppc64_cpu —smt=<level>, the SMT level is not retained after
>> cpu core add.
> 
> That's because ppc64_cpu is not using the sysfs SMT control file, it's
> just onlining/offlining threads manually.
> 
> If you run:
> $ ppc64_cpu --smt=4 
> 
> And then also do:
> 
> $ echo 4 > /sys/devices/system/cpu/smt/control
> 
> It should work as expected?

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

- Sachin