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Message-ID: <Ztqp-SUinu8C9a-P@R5WKVNH4JW> Date: Fri, 6 Sep 2024 09:06:33 +0200 From: Morten Rasmussen <morten.rasmussen@....com> To: Yicong Yang <yangyicong@...wei.com> Cc: Pierre Gondois <pierre.gondois@....com>, yangyicong@...ilicon.com, linuxppc-dev@...ts.ozlabs.org, bp@...en8.de, dave.hansen@...ux.intel.com, mingo@...hat.com, linux-arm-kernel@...ts.infradead.org, mpe@...erman.id.au, peterz@...radead.org, tglx@...utronix.de, sudeep.holla@....com, will@...nel.org, catalin.marinas@....com, x86@...nel.org, linux-kernel@...r.kernel.org, dietmar.eggemann@....com, gregkh@...uxfoundation.org, rafael@...nel.org, jonathan.cameron@...wei.com, prime.zeng@...ilicon.com, linuxarm@...wei.com, xuwei5@...wei.com, guohanjun@...wei.com Subject: Re: [PATCH v5 3/4] arm64: topology: Support SMT control on ACPI based system Hi Yicong, On Thu, Sep 05, 2024 at 08:02:20PM +0800, Yicong Yang wrote: > On 2024/9/5 16:34, Pierre Gondois wrote: > > Hello Yicong, > > > > If a platform has CPUs with: > > - 1 thread > > - X (!= 1) threads > > Then I think that the asymmetry is not detected > > Ah ok, I only handle the case where there are several thread numbers except no SMT CPUs in the > system. For this case I was thinking we don't need to handle this since there's only one kind > of SMT core in the system, control should works fine for the SMT CPU clusters and we may not > care about the CPUs with no SMT. > > Below code should handle the case if we initialize the max_smt_thread_num to 0. I also > reword the warning messages to match the fact. For heterogeneous SMT topology we still > support control SMT by on/off toggle but not fully support setting the thread number. > > int max_smt_thread_num = 0; > [...] > /* > * This should be a short loop depending on the number of heterogeneous > * CPU clusters. Typically on a homogeneous system there's only one > * entry in the XArray. > */ > xa_for_each(&hetero_cpu, hetero_id, entry) { > /* > * If max_smt_thread_num has been initialized and doesn't match > * the thread number of this entry, then the system has > * heterogeneous SMT topology. > */ > if (entry->thread_num != max_smt_thread_num && max_smt_thread_num) > pr_warn_once("Heterogeneous SMT topology is partly supported by SMT control\n"); What does 'partly supported' mean here? If the SMT control doesn't work as intended for this topology, I don't think it should be enabled for it. Morten
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