Hi Lukasz,
On 19. 2. 13. 오후 10:35, Lukasz Luba wrote:
> Hi Steven,
>
> On 2/13/19 12:14 AM, Steven Rostedt wrote:
>> On Tue, 12 Feb 2019 23:23:57 +0100
>> Lukasz Luba <l.l...@partner.samsung.com> 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 <l.l...@partner.samsung.com>
>>> ---
>>> 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 <cw00.c...@samsung.com>
>>> 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>
>>
>>
>>
>
>
I agree that trace point is necessary for devfreq framework.
Reviewed-by: Chanwoo Choi <cw00.c...@samsung.com>
--
Best Regards,
Chanwoo Choi
Samsung Electronics
