Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [PATCH 1/3] thermal/cpu-cooling, sched/core: Cleanup thermal pressure definition | Date | Sun, 05 Jul 2020 15:19:44 +0100 |
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Sorry for getting back to this only now;
On 22/06/20 09:37, Vincent Guittot wrote: > On Sun, 21 Jun 2020 at 00:28, Valentin Schneider <valentin.schneider@arm.com> wrote: >> On 20/06/20 18:49, Ionela Voinescu wrote: >> > On Thursday 18 Jun 2020 at 17:03:24 (+0200), Vincent Guittot wrote: >> >> Having this weak function declared in cpufreq_cooling is weird. This >> >> means that we will have to do so for each one that wants to use it. >> >> >> >> Can't you declare an empty function in a common header file ? >> > >> > Do we expect anyone other than cpufreq_cooling to call >> > arch_set_thermal_pressure()? >> > >> > I'm not against any of the options, either having it here as a week >> > default definition (same as done for arch_set_freq_scale() in cpufreq.c) >> > or in a common header (as done for arch_scale_freq_capacity() in sched.h). >> > >> >> Same thoughts here; I was going for the arch_set_freq_scale() way. >> >> > But for me, Valentin's implementation seems more natural as setters are >> > usually only called from within the framework that does the control >> > (throttling for thermal or frequency setting for cpufreq) and we >> > probably want to think twice if we want to call them from other places. >> > >> >> Well TBH I was tempted to go the other way and keep the definition in >> core.c, given a simple per-cpu value is fairly generic. More precisely, it > > Having all definitions in the same place is my main concern here. > If topology.c defines arch_set_thermal_pressure it should also provide > the empty function when the feature is not available or possible > instead of relying of each user of the interface to define a weak > function just in case. >
include/linux/sched/topology.h already defines a stub for arch_scale_thermal_pressure(), I suppose we could have one for arch_set_thermal_pressure() there.
That would require having something like
#define arch_set_thermal_pressure topology_set_thermal_pressure
in the arm & arm64 include/asm/topology.h headers, with topology_set_thermal_pressure() being what arch_set_thermal_pressure() currently is in this patchset.
This would set an odd precedent in that so far we only ever had to #define getter functions, the setters being either: - entirely contained within arch_topology. (for the CPU scale) - defined in arch_topology, declared in cpufreq and contained there (for the freq scale).
It made the most sense to me to follow the arch_set_freq_scale() pattern and contain the thermal pressure setter within cpufreq_cooling, especially since I didn't see a strong point in breaking the current patterns.
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