Add trace event to capture the moment of the call for updating the thermal
pressure value. It's helpful to investigate how often those events occurs
in a system dealing with throttling. This trace event is needed since the
old 'cdev_update' might not be used by some drivers. Also, the new trace
event shows capacity value, not a cooling state.
We already have a trace point 'pelt_thermal_tp' which after a change to
trace event can be paired with this new 'thermal_pressure_update' and
derive more insight what is going on in the system under pressure
(and why).
Signed-off-by: Lukasz Luba <[email protected]>
---
drivers/base/arch_topology.c | 4 ++++
include/trace/events/thermal.h | 19 +++++++++++++++++++
2 files changed, 23 insertions(+)
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)
+ ),
+
+ 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,
--
2.17.1
On 4/21/22 00:44, Steven Rostedt wrote:
> On Tue, 19 Apr 2022 17:48:01 +0100
> Lukasz Luba <[email protected]> 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
On Tue, 19 Apr 2022 17:48:01 +0100
Lukasz Luba <[email protected]> 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,