Messages in this thread | | | Subject | Re: [Patch v5 2/6] sched/fair: Add infrastructure to store and update instantaneous thermal pressure | From | Dietmar Eggemann <> | Date | Wed, 6 Nov 2019 13:50:26 +0100 |
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On 05/11/2019 22:53, Ionela Voinescu wrote: > On Tuesday 05 Nov 2019 at 16:29:32 (-0500), Thara Gopinath wrote: >> On 11/05/2019 04:15 PM, Ionela Voinescu wrote: >>> On Tuesday 05 Nov 2019 at 16:02:00 (-0500), Thara Gopinath wrote: >>>> On 11/05/2019 03:21 PM, Ionela Voinescu wrote: >>>>> Hi Thara, >>>>> >>>>> On Tuesday 05 Nov 2019 at 13:49:42 (-0500), Thara Gopinath wrote: >>>>> [...] >>>>>> +static void trigger_thermal_pressure_average(struct rq *rq) >>>>>> +{ >>>>>> +#ifdef CONFIG_SMP >>>>>> + update_thermal_load_avg(rq_clock_task(rq), rq, >>>>>> + per_cpu(thermal_pressure, cpu_of(rq))); >>>>>> +#endif >>>>>> +} >>>>> >>>>> Why did you decide to keep trigger_thermal_pressure_average and not >>>>> call update_thermal_load_avg directly? >>>>> >>>>> For !CONFIG_SMP you already have an update_thermal_load_avg function >>>>> that does nothing, in kernel/sched/pelt.h, so you don't need that >>>>> ifdef. >>>> Hi, >>>> >>>> Yes you are right. But later with the shift option added, I shift >>>> rq_clock_task(rq) by the shift. I thought it is better to contain it in >>>> a function that replicate it in three different places. I can remove the >>>> CONFIG_SMP in the next version. >>> >>> You could still keep that in one place if you shift the now argument of >>> ___update_load_sum instead. >> >> No. I cannot do this. The authors of the pelt framework prefers not to >> include a shift parameter there. I had discussed this with Vincent earlier. >> > > Right! I missed Vincent's last comment on this in v4. > > I would argue that it's more of a PELT parameter than a CFS parameter > :), where it's currently being used. I would also argue that's more of a > PELT parameter than a thermal parameter. It controls the PELT time > progression for the thermal signal, but it seems more to configure the > PELT algorithm, rather than directly characterize thermals. > > In any case, it only seemed to me that adding a wrapper function for > this purpose only was not worth doing.
Coming back to the v4 discussion https://lore.kernel.org/r/379d23e5-79a5-9d90-0fb6-125d9be85e99@arm.com
There is no API between pelt.c and other parts of the scheduler/kernel so why should we keep an unnecessary parameter and wrapper functions?
There is also no abstraction, update_thermal_load_avg() in pelt.c even carries '_thermal_' in its name.
So why not define this shift value '[sched_|pelt_]thermal_decay_shift' there as well? It belongs to update_thermal_load_avg().
All call sites of update_thermal_load_avg() use 'rq_clock_task(rq) >> sched_thermal_decay_shift' so I don't see the need to pass it in.
IMHO, preparing for eventual code changes (e.g. parsing different now values) is not a good practice in the kernel. Keeping the code small and tidy is.
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