Messages in this thread | | | Date | Fri, 20 Apr 2018 15:51:20 +0100 | From | Quentin Perret <> | Subject | Re: [RFC PATCH v2 4/6] sched/fair: Introduce an energy estimation helper function |
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On Wednesday 18 Apr 2018 at 17:23:16 (+0800), Leo Yan wrote: > On Fri, Apr 06, 2018 at 04:36:05PM +0100, Dietmar Eggemann wrote: > > [...] > > > +/* > > + * Estimates the system level energy assuming that p wakes-up on dst_cpu. > > + * > > + * compute_energy() is safe to call only if an energy model is available for > > + * the platform, which is when sched_energy_enabled() is true. > > + */ > > +static unsigned long compute_energy(struct task_struct *p, int dst_cpu) > > +{ > > + unsigned long util, max_util, sum_util; > > + struct capacity_state *cs; > > + unsigned long energy = 0; > > + struct freq_domain *fd; > > + int cpu; > > + > > + for_each_freq_domain(fd) { > > + max_util = sum_util = 0; > > + for_each_cpu_and(cpu, freq_domain_span(fd), cpu_online_mask) { > > + util = cpu_util_next(cpu, p, dst_cpu); > > + util += cpu_util_dl(cpu_rq(cpu)); > > + max_util = max(util, max_util); > > + sum_util += util; > > + } > > + > > + /* > > + * Here we assume that the capacity states of CPUs belonging to > > + * the same frequency domains are shared. Hence, we look at the > > + * capacity state of the first CPU and re-use it for all. > > + */ > > + cpu = cpumask_first(freq_domain_span(fd)); > > + cs = find_cap_state(cpu, max_util); > > + energy += cs->power * sum_util / cs->cap; > > I am a bit worry about the resolution issue, especially when the > capacity value is a quite high value and sum_util is a minor value.
Good point. As of now, the cs->power values happen to be in micro-watts for the platforms we've been testing with, so they're typically high enough to avoid significant resolution problem I guess.
Now, the energy model code has to be reworked significantly as we have to remove the dependency on PM_OPP, so I'll try to make sure to keep this issue in mind for the next version.
Thanks, Quentin
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