On 14-03-19, 10:40, Rafael J. Wysocki wrote: > On Thu, Mar 14, 2019 at 10:28 AM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > > > On Thu, Mar 14, 2019 at 7:43 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote: > > > > > > Currently we call the cpufreq transition notifiers once for each CPU of > > > the policy->cpus cpumask, which isn't that efficient. > > > > Why isn't it efficient? > > > > Transitions are per-policy anyway, so if something needs to be done > > for each CPU in the policy, it doesn't matter too much which part of > > the code carries out the iteration. > > > > I guess some notifiers need to know what other CPUs there are in the > > policy? If so, then why? > > > > > This patchset tries to simplify that by adding another field in struct cpufreq_freqs, > > > cpus, so the callback has all the information available with a single > > > call for each policy. > > > > Well, you can argue that the core is simplified by it somewhat, but > > the notifiers aren't. They actually get more complex, conceptually > > too, because they now need to worry about offline vs online CPUs etc. > > > > Also I wonder why you decided to pass a cpumask in freqs instead of > > just passing a policy pointer. If you change things from per-CPU to > > per-policy, passing the whole policy seems more natural. > > It also looks to me like all that needs to be one patch, or you have > the ugly transition situation in which notifiers are still invoked for > each CPU, but they assume to be invoked once per policy. I assumed that calling something like set_cyc2ns_scale() in x86 multiple times for each CPU shouldn't be that bad even if the frequency changes only once, but such things may actually have side-effects. I should merged them all. -- viresh
