Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v7 02/14] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling | Date | Fri, 28 Sep 2018 10:23:42 +0200 |
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On Thursday, September 27, 2018 2:17:49 PM CEST Quentin Perret wrote: > Hi Rafael, > > Very sorry for the late reply ... > > On Tuesday 18 Sep 2018 at 23:33:22 (+0200), Rafael J. Wysocki wrote: > [...] > > The new "type" argument should be documented. > > > > Also IMO using the special enum for it is quite confusing, because you > > ever only check one value from it directly. What would be wrong with > > using a plain "bool" instead? > > So, this part of the code was originally proposed by Peter. I basically > took it from the following message (hence the Suggested-by) which was > fine by me: > > https://lore.kernel.org/lkml/20180709120138.GQ2494@hirez.programming.kicks-ass.net/ > > Also, one of the things that has been mentioned during reviews was that > other clients (such as cpuidle, IIRC) could potentially be interested > in a 'global' cpu util value. And since those clients might have > different needs than EAS or sugov, they might need a new entry in the > enum. > > So that's probably the main argument for the enum, it is easy to extend.
OK, so please document the enum type.
> [...] > > > +static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu) > > > +{ > > > + struct rq *rq = cpu_rq(sg_cpu->cpu); > > > + unsigned long util = cpu_util_cfs(rq); > > > + > > > + sg_cpu->max = arch_scale_cpu_capacity(NULL, sg_cpu->cpu); > > > + sg_cpu->bw_dl = cpu_bw_dl(rq); > > > + > > > + return schedutil_freq_util(sg_cpu->cpu, util, FREQUENCY_UTIL); > > > > If you add a "max" argument to schedutil_freq_util(), you can avoid > > the second (and arguably redundant) evaluation of > > arch_scale_cpu_capacity() in there. > > OK > > [...] > > > +enum schedutil_type { > > > + FREQUENCY_UTIL, > > > + ENERGY_UTIL, > > > +}; > > > > As I said above, I would just use "bool" instead of this new enum (it > > has two values too) or the new type needs to be documented. > > As I said above, the enum has the good side of being easier to extend. > So, if we care about that, I guess I'd rather add a doc for the new > type.
Right, so please add a kerneldoc description here.
> > > + > > > #ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL > > > +unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs, > > > + enum schedutil_type type); > > > + > > > static inline unsigned long cpu_bw_dl(struct rq *rq) > > > { > > > return (rq->dl.running_bw * SCHED_CAPACITY_SCALE) >> BW_SHIFT; > > > @@ -2199,6 +2207,12 @@ static inline unsigned long cpu_util_rt(struct rq *rq) > > > { > > > return READ_ONCE(rq->avg_rt.util_avg); > > > } > > > +#else /* CONFIG_CPU_FREQ_GOV_SCHEDUTIL */ > > > +static inline unsigned long schedutil_freq_util(int cpu, unsigned long util, > > > + enum schedutil_type type) > > > +{ > > > + return util; > > > +} > > > #endif > > > > And I would add a wrapper around schedutil_freq_util(), called say > > schedutil_energy_util(), that would pass a specific value as the > > "type". > > OK, that's fine by me. > > Other than that, do you think these changes could be done later ? Or do > you see that as mandatory before the patches can be picked up ?
Documenting things properly is absolutely required.
The other changes suggested by me are rather straightforward, so why would it be a problem to make them right away if you agree to make them?
Thanks, Rafael
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