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    SubjectRe: [PATCH v2 4/7] sched/fair: Introduce sched_smt_siblings_idle()
    On Wed, Dec 28, 2022 at 11:29:52PM +0800, Chen Yu wrote:
    > On 2022-12-23 at 21:28:50 -0800, Ricardo Neri wrote:
    > > On Thu, Dec 22, 2022 at 04:56:22PM +0000, Valentin Schneider wrote:
    > > > On 22/11/22 12:35, Ricardo Neri wrote:
    > > > > Architectures that implement arch_asym_cpu_priority() may need to know the
    > > > > idle state of the SMT siblings of a CPU. The scheduler has this information
    > > > > and functionality. Expose it.
    > > > >
    > > > > Move the existing functionality outside of the NUMA code.
    > > > >
    > > >
    > > > test_idle_cores() does something similar without an iteration, did you
    > > > consider using that instead?
    > >
    > > IIUC, test_idle_cores() returns true if there is at least one idle core in
    > > the package. In my case, I need to know the idle state of only the SMT
    > > siblings of a specific CPU. Am I missing something?
    > >
    > I guess a similar one is select_idle_core(), but it also consider the CPU with
    > SCHED_IDLE task as idle. Is CPU with SCHED_IDLE task a candidate in your
    > scenario?

    However, we are not looking for an idle CPU. We want to know the idle state of
    the siblings of a CPU. I see that select_idle_core() uses available_idle_cpu(),
    which in turn uses idle_cpu(). is_core_idle() also uses it.

    As per 943d355d7fee ("sched/core: Distinguish between idle_cpu() calls based on
    desired effect, introduce available_idle_cpu()") the load balancer can just
    call idle_cpu().

    Thanks and BR,
    Ricardo

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