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SubjectRe: [PATCH] arch_topology: Trace the update thermal pressure
On Tue, 19 Apr 2022 17:48:01 +0100
Lukasz Luba <lukasz.luba@arm.com> wrote:

> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 1d6636ebaac5..4f0392de3081 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -19,6 +19,8 @@
> #include <linux/rcupdate.h>
> #include <linux/sched.h>
>
> +#include <trace/events/thermal.h>
> +
> static DEFINE_PER_CPU(struct scale_freq_data __rcu *, sft_data);
> static struct cpumask scale_freq_counters_mask;
> static bool scale_freq_invariant;
> @@ -195,6 +197,8 @@ void topology_update_thermal_pressure(const struct cpumask *cpus,
>
> th_pressure = max_capacity - capacity;
>
> + trace_thermal_pressure_update(cpu, th_pressure);
> +
> for_each_cpu(cpu, cpus)
> WRITE_ONCE(per_cpu(thermal_pressure, cpu), th_pressure);
> }
> diff --git a/include/trace/events/thermal.h b/include/trace/events/thermal.h
> index 8a5f04888abd..1bf08ee1a25b 100644
> --- a/include/trace/events/thermal.h
> +++ b/include/trace/events/thermal.h
> @@ -65,6 +65,25 @@ TRACE_EVENT(cdev_update,
> TP_printk("type=%s target=%lu", __get_str(type), __entry->target)
> );
>
> +TRACE_EVENT(thermal_pressure_update,
> +
> + TP_PROTO(int cpu, unsigned long thermal_pressure),
> +
> + TP_ARGS(cpu, thermal_pressure),
> +
> + TP_STRUCT__entry(
> + __field(int, cpu)
> + __field(unsigned long, thermal_pressure)

Note, it is always best to place the bigger object before the smaller one
(when not properly aligned), as that will help to prevent structure
"holes". That is:

__field(unsigned long, thermal_pressure)
__field(int, cpu)


Otherwise, you are pretty much guaranteed to have a 4 byte hole between cpu
and thermal_pressure on 64 bit machines.

Also, for the warning you got from the test robot, if you are using this in
a module and defining it in the core kernel, you need to add:

EXPORT_TRACEPOINT_SYMBOL_GPL(thermal_pressure_update);

Somewhere in the C file that includes this file and defines
CREATE_TRACE_POINTS.

-- Steve



> + ),
> +
> + TP_fast_assign(
> + __entry->cpu = cpu;
> + __entry->thermal_pressure = thermal_pressure;
> + ),
> +
> + TP_printk("cpu=%d thermal_pressure=%lu", __entry->cpu, __entry->thermal_pressure)
> +);
> +
> TRACE_EVENT(thermal_zone_trip,
>
> TP_PROTO(struct thermal_zone_device *tz, int trip,

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