Re: [RESEND][PATCH v2 3/3] schedutil: trace: Add tracing to capture filter out requests

Lukasz Luba
2023-06-20T18:08:02Z

Hi Rafael,

On 6/20/23 18:40, Rafael J. Wysocki wrote:
> On Mon, May 22, 2023 at 4:57 PM Lukasz Luba <lukasz.luba@arm.com> wrote:
>>
>> Some of the frequency update requests coming form the task scheduler
>> might be filter out. It can happen when the previous request was served
>> not that long ago (in a period smaller than provided by the cpufreq driver
>> as minimum for frequency update). In such case, we want to know if some of
>> the frequency updates cannot make through.
>> Export the new tracepoint as well. That would allow to handle it by a
>> toolkit for trace analyzes.
>>
>> Reported-by: kernel test robot <lkp@intel.com> # solved tricky build
>> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
>> ---
>> include/trace/events/sched.h | 4 ++++
>> kernel/sched/cpufreq_schedutil.c | 10 ++++++++--
>> 2 files changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
>> index dbfb30809f15..e34b7cd5de73 100644
>> --- a/include/trace/events/sched.h
>> +++ b/include/trace/events/sched.h
>> @@ -739,6 +739,10 @@ DECLARE_TRACE(uclamp_update_tsk_tp,
>> TP_PROTO(struct task_struct *tsk, int uclamp_id, unsigned int value),
>> TP_ARGS(tsk, uclamp_id, value));
>>
>> +DECLARE_TRACE(schedutil_update_filtered_tp,
>> + TP_PROTO(int cpu),
>> + TP_ARGS(cpu));
>> +
>> #endif /* _TRACE_SCHED_H */
>>
>> /* This part must be outside protection */
>> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
>> index f462496e5c07..4f9daf258a65 100644
>> --- a/kernel/sched/cpufreq_schedutil.c
>> +++ b/kernel/sched/cpufreq_schedutil.c
>> @@ -6,6 +6,8 @@
>> * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> */
>>
>> +EXPORT_TRACEPOINT_SYMBOL_GPL(schedutil_update_filtered_tp);
>> +
>> #define IOWAIT_BOOST_MIN (SCHED_CAPACITY_SCALE / 8)
>>
>> struct sugov_tunables {
>> @@ -318,8 +320,10 @@ static inline bool sugov_update_single_common(struct sugov_cpu *sg_cpu,
>>
>> ignore_dl_rate_limit(sg_cpu);
>>
>> - if (!sugov_should_update_freq(sg_cpu->sg_policy, time))
>> + if (!sugov_should_update_freq(sg_cpu->sg_policy, time)) {
>> + trace_schedutil_update_filtered_tp(sg_cpu->cpu);
>
> It looks like the tracepoint can be added to
> sugov_should_update_freq() for less code duplication.
>

Make sense. I will move that trace there.

In such case, of movement that trace call...
Based on your comment for patch 2/3 I got impression
that you still want it. For me it looks more 'aligned' w/ that
patch 2/3. The two functions code flows:
sugov_update_shared() and sugov_update_single_common() - how
they call and interpret result from
sugov_should_update_freq() - is more clear IMO.

So I will keep that patch 2/3 in the next version. Although,
if you don't like it - please tell me and I will drop it.

Thanks for the review!

Lukasz