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SubjectRe: [PATCH] arch_topology: Trace the update thermal pressure
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On 4/21/22 00:44, Steven Rostedt wrote:
> 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
>
>

Thank you Steve, I'll swap those fields and add the needed export.
I have to go through those older trace events in that file and
understand if they are correct, since I just followed the pattern
in 'cdev_update'.

Regards,
Lukasz

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