Re: [PATCH 3/3] ACPI: cpufreq: Add ITMT support when CPPC enabled for Zhaoxin CPUs

[Tony W Wang-oc]

On 2024/1/18 06:51, Ricardo Neri wrote:
> [这封邮件来自外部发件人]
>
> On Thu, Dec 28, 2023 at 03:57:05PM +0800, Tony W Wang-oc wrote:
> > For Zhaoxin CPUs, the cores' highest frequencies may be different, which
> > means that cores may run at different max frequencies,
> >
> > According to ACPI-spec6 chapter 8.4.7, the per-core highest frequency
> > value can be obtained via cppc.
> >
> > The core with the higher frequency have better performance, which can be
> > called as preferred core. And better performance can be achieved by
> > making the scheduler to run tasks on these preferred cores.
> >
> > The cpufreq driver can use the highest frequency value as the prioriy of
> > core to make the scheduler try to get better performace. More specifically,
> > in the acpi-cpufreq driver use cppc_get_highest_perf() to get highest
> > frequency value of each core, use sched_set_itmt_core_prio() to set
> > highest frequency value as core priority, and use sched_set_itmt_support()
> > provided by ITMT to tell the scheduler to favor on the preferred cores.
> >
> > Signed-off-by: Tony W Wang-oc <TonyWWang-oc@xxxxxxxxxxx>
> > ---
> >   drivers/cpufreq/acpi-cpufreq.c | 56 +++++++++++++++++++++++++++++++++-
> >   1 file changed, 55 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> > index 37f1cdf46d29..f4c1ff9e4bb0 100644
> > --- a/drivers/cpufreq/acpi-cpufreq.c
> > +++ b/drivers/cpufreq/acpi-cpufreq.c
> > @@ -663,8 +663,56 @@ static u64 get_max_boost_ratio(unsigned int cpu)
> >
> >        return div_u64(highest_perf << SCHED_CAPACITY_SHIFT, nominal_perf);
> >   }
> > +
> > +/* The work item is needed to avoid CPU hotplug locking issues */
> > +static void sched_itmt_work_fn(struct work_struct *work)
> > +{
> > +     sched_set_itmt_support();
> > +}
> > +
> > +static DECLARE_WORK(sched_itmt_work, sched_itmt_work_fn);
> > +
> > +static void set_itmt_prio(int cpu)
> > +{
> > +     static bool cppc_highest_perf_diff;
> > +     static struct cpumask core_prior_mask;
> > +     u64 highest_perf;
> > +     static u64 max_highest_perf = 0, min_highest_perf = U64_MAX;
> > +     int ret;
> > +
> > +     ret = cppc_get_highest_perf(cpu, &highest_perf);
> > +     if (ret)
> > +             return;
> > +
> > +     sched_set_itmt_core_prio(highest_perf, cpu);
> > +     cpumask_set_cpu(cpu, &core_prior_mask);
> > +
> > +     if (max_highest_perf <= min_highest_perf) {
> > +             if (highest_perf > max_highest_perf)
> > +                     max_highest_perf = highest_perf;
> > +
> > +             if (highest_perf < min_highest_perf)
> > +                     min_highest_perf = highest_perf;
> > +
> > +             if (max_highest_perf > min_highest_perf) {
> > +                     /*
> > +                      * This code can be run during CPU online under the
> > +                      * CPU hotplug locks, so sched_set_itmt_support()
> > +                      * cannot be called from here.  Queue up a work item
> > +                      * to invoke it.
> > +                      */
> > +                     cppc_highest_perf_diff = true;
> > +             }
> > +     }
> > +
> > +     if (cppc_highest_perf_diff && cpumask_equal(&core_prior_mask, cpu_online_mask)) {
> > +             pr_debug("queue a work to set itmt enabled\n");
> > +             schedule_work(&sched_itmt_work);
> > +     }
> > +}
> sched_itmt_work and this function is a duplicate of what the intel_pstate
> driver already does. It might be good if consolidate in a single place
> if you are going to pursue this approach.

Thanks for your suggestion, will change the patch code in v2.

Sorry for late.