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SubjectRe: [PATCH v3 15/24] thermal: intel: hfi: Report the IPC class score of a CPU
On Tue, Feb 7, 2023 at 6:02 AM Ricardo Neri
<ricardo.neri-calderon@linux.intel.com> wrote:
>
> Implement the arch_get_ipcc_score() interface of the scheduler. Use the
> performance capabilities of the extended Hardware Feedback Interface table
> as the IPC score.
>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Ionela Voinescu <ionela.voinescu@arm.com>
> Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
> Cc: Len Brown <len.brown@intel.com>
> Cc: Lukasz Luba <lukasz.luba@arm.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Tim C. Chen <tim.c.chen@intel.com>
> Cc: Valentin Schneider <vschneid@redhat.com>
> Cc: x86@kernel.org
> Cc: linux-pm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> ---
> Changes since v2:
> * None
>
> Changes since v1:
> * Adjusted the returned HFI class (which starts at 0) to match the
> scheduler IPCC class (which starts at 1). (PeterZ)
> * Used the new interface names.
> ---
> arch/x86/include/asm/topology.h | 2 ++
> drivers/thermal/intel/intel_hfi.c | 27 +++++++++++++++++++++++++++
> 2 files changed, 29 insertions(+)
>
> diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
> index ffcdac3f398f..c4fcd9c3c634 100644
> --- a/arch/x86/include/asm/topology.h
> +++ b/arch/x86/include/asm/topology.h
> @@ -229,8 +229,10 @@ void init_freq_invariance_cppc(void);
>
> #if defined(CONFIG_IPC_CLASSES) && defined(CONFIG_INTEL_HFI_THERMAL)
> void intel_hfi_update_ipcc(struct task_struct *curr);
> +unsigned long intel_hfi_get_ipcc_score(unsigned short ipcc, int cpu);
>
> #define arch_update_ipcc intel_hfi_update_ipcc
> +#define arch_get_ipcc_score intel_hfi_get_ipcc_score
> #endif /* defined(CONFIG_IPC_CLASSES) && defined(CONFIG_INTEL_HFI_THERMAL) */
>
> #endif /* _ASM_X86_TOPOLOGY_H */
> diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c
> index 530dcf57e06e..fa9b4a678d92 100644
> --- a/drivers/thermal/intel/intel_hfi.c
> +++ b/drivers/thermal/intel/intel_hfi.c
> @@ -206,6 +206,33 @@ void intel_hfi_update_ipcc(struct task_struct *curr)
> curr->ipcc = msr.split.classid + 1;
> }
>
> +unsigned long intel_hfi_get_ipcc_score(unsigned short ipcc, int cpu)
> +{
> + unsigned short hfi_class;

It looks like the variable above is only used to save a subtraction or
addition of 1 to something going forward.

> + int *scores;
> +
> + if (cpu < 0 || cpu >= nr_cpu_ids)
> + return -EINVAL;
> +
> + if (ipcc == IPC_CLASS_UNCLASSIFIED)
> + return -EINVAL;
> +
> + /*
> + * Scheduler IPC classes start at 1. HFI classes start at 0.
> + * See note intel_hfi_update_ipcc().
> + */
> + hfi_class = ipcc - 1;
> +
> + if (hfi_class >= hfi_features.nr_classes)

Personally, I would do

if (ipcc >= hfi_features.nr_classes + 1)

here and ->

> + return -EINVAL;
> +
> + scores = per_cpu_ptr(hfi_ipcc_scores, cpu);
> + if (!scores)
> + return -ENODEV;
> +

-> scores[ipcc - 1]

below.

> + return READ_ONCE(scores[hfi_class]);

And why does this need to use READ_ONCE()?

> +}
> +
> static int alloc_hfi_ipcc_scores(void)
> {
> if (!cpu_feature_enabled(X86_FEATURE_ITD))
> --

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