Hi Steven,
On 2/13/19 12:14 AM, Steven Rostedt wrote:
> On Tue, 12 Feb 2019 23:23:57 +0100
> Lukasz Luba <[email protected]> wrote:
>
>> The patch adds a new file for with trace events for devfreq
>> framework. They are used for performance analysis of the framework.
>> It also contains updates in MAINTAINERS file adding new entry for
>> devfreq maintainers.
>>
>> Signed-off-by: Lukasz Luba <[email protected]>
>> ---
>> MAINTAINERS | 1 +
>> include/trace/events/devfreq.h | 39 +++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 40 insertions(+)
>> create mode 100644 include/trace/events/devfreq.h
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 9919840..c042fda 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -4447,6 +4447,7 @@ S: Maintained
>> F: drivers/devfreq/
>> F: include/linux/devfreq.h
>> F: Documentation/devicetree/bindings/devfreq/
>> +F: include/trace/events/devfreq.h
>>
>> DEVICE FREQUENCY EVENT (DEVFREQ-EVENT)
>> M: Chanwoo Choi <[email protected]>
>> diff --git a/include/trace/events/devfreq.h b/include/trace/events/devfreq.h
>> new file mode 100644
>> index 0000000..fec9304
>> --- /dev/null
>> +++ b/include/trace/events/devfreq.h
>> @@ -0,0 +1,39 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#undef TRACE_SYSTEM
>> +#define TRACE_SYSTEM devfreq
>> +
>> +#if !defined(_TRACE_DEVFREQ_H) || defined(TRACE_HEADER_MULTI_READ)
>> +#define _TRACE_DEVFREQ_H
>> +
>> +#include <linux/devfreq.h>
>> +#include <linux/tracepoint.h>
>> +
>> +TRACE_EVENT(devfreq_monitor,
>> + TP_PROTO(const char *dev_name, unsigned long freq,
>> + unsigned int polling_ms, unsigned long busy_time,
>> + unsigned long total_time),
>> +
>> + TP_ARGS(dev_name, freq, polling_ms, busy_time, total_time),
>> +
>> + TP_STRUCT__entry(
>> + __string(dev_name, dev_name)
>> + __field(unsigned long, freq)
>> + __field(unsigned int, polling_ms)
>> + __field(unsigned int, load)
>> + ),
>> +
>> + TP_fast_assign(
>> + __assign_str(dev_name, dev_name);
>> + __entry->freq = freq;
>> + __entry->polling_ms = polling_ms;
>> + __entry->load = (100 * busy_time) / total_time;
>
> How critical is the code that this trace event is called in. If it is
> not that critical (it is a slow path), then this is fine, but if this
> is not a slow path (something triggered 100 HZ or less), then I would
> recommend moving the above calculation to TP_printk(). A divide is a
> slow operation, and is best to do that in the post processing. The
> current location does the divide at the time of the tracepoint is
> called.
I wasn't aware of these two stages, good to know.
I will move it to TP_printk().
>
> I would also have a check to make sure that total_time is not zero
> here, otherwise that could be bad.
>
> __entry->busy_time = busy_time;
> __entry->total_time = total_time;
>
>> + ),
>> +
>> + TP_printk("dev_name=%s freq=%lu polling_ms=%u load=%u",
>
>
>> + __get_str(dev_name), __entry->freq, __entry->polling_ms,
>
> __entry->total_time == 0 ? 100 :
> __entry->busy_time / __entry->total_time)
Thank you for the review.
I will add this check.
Regards,
Lukasz
>
> -- Steve
>
>> + __entry->load)
>> +);
>> +#endif /* _TRACE_DEVFREQ_H */
>> +
>> +/* This part must be outside protection */
>> +#include <trace/define_trace.h>
>
>
>
