Messages in this thread Patch in this message | | | From | Lukasz Luba <> | Subject | [PATCH v2] arch_topology: Trace the update thermal pressure | Date | Mon, 25 Apr 2022 14:53:17 +0100 |
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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).
Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> --- Hi all,
This v2 solves the issue reported by build robot. After experiments and checks I decided to not add the EXPORT_TRACEPOINT_SYMBOL_GPL(thermal_pressure_update) The trace event shouldn't be used by modules, since they use the exported update function: EXPORT_SYMBOL_GPL(topology_update_thermal_pressure) which calls that trace event internally. The code duplication for updating thermal pressure in a modules is not recommended - that was the goal of introducing topology_update_thermal_pressure().
Changes in v2: - as suggested by Steve, I have swapped the fields - a new trace header, so no conflicts with thermal.h - added CREATE_TRACE_POINTS before header
The v1 and discussion can be found here at: https://lore.kernel.org/lkml/20220419164801.29078-1-lukasz.luba@arm.com/
Regards, Lukasz
drivers/base/arch_topology.c | 5 +++++ include/trace/events/thermal_pressure.h | 29 +++++++++++++++++++++++++ 2 files changed, 34 insertions(+) create mode 100644 include/trace/events/thermal_pressure.h
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 1d6636ebaac5..20bdad18dccd 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -19,6 +19,9 @@ #include <linux/rcupdate.h> #include <linux/sched.h> +#define CREATE_TRACE_POINTS +#include <trace/events/thermal_pressure.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 +198,8 @@ 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_pressure.h b/include/trace/events/thermal_pressure.h new file mode 100644 index 000000000000..b68680201360 --- /dev/null +++ b/include/trace/events/thermal_pressure.h @@ -0,0 +1,29 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM thermal_pressure + +#if !defined(_TRACE_THERMAL_PRESSURE_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_THERMAL_PRESSURE_H + +#include <linux/tracepoint.h> + +TRACE_EVENT(thermal_pressure_update, + TP_PROTO(int cpu, unsigned long thermal_pressure), + TP_ARGS(cpu, thermal_pressure), + + TP_STRUCT__entry( + __field(unsigned long, thermal_pressure) + __field(int, cpu) + ), + + TP_fast_assign( + __entry->thermal_pressure = thermal_pressure; + __entry->cpu = cpu; + ), + + TP_printk("cpu=%d thermal_pressure=%lu", __entry->cpu, __entry->thermal_pressure) +); +#endif /* _TRACE_THERMAL_PRESSURE_H */ + +/* This part must be outside protection */ +#include <trace/define_trace.h> -- 2.17.1
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