On Thu, Mar 10, 2016 at 10:44:21AM +0700, Vincent Guittot wrote: > We have the arch_scale_freq_capacity function that is arch dependent > and can be used to merge the 2 formula that were described by peter > above. > By default, arch_scale_freq_capacity return SCHED_CAPACITY_SCALE which > is max capacity > but when arch_scale_freq_capacity is defined by an architecture, > arch_scale_freq_capacity returns current_freq * max_capacity/max_freq However, current_freq is a very fluid thing, it might (and will) change very rapidly on some platforms. This is the same point I made earlier, you cannot try and divide out current_freq from the invariant measure. > so can't we use arch_scale_freq in your formula ? Taking your formula > above it becomes: > next_freq = 1.25 * current_freq * util / arch_scale_freq_capacity() No, that cannot work, nor makes any sense, per the above. > With invariance feature, we have: > > next_freq = 1.25 * current_freq * util / (current_freq*max_capacity/max_freq) > = 1.25 * util * max_freq / max > > which is the formula that has to be used with frequency invariant > utilization. Wrong, you cannot talk about current_freq in the invariant case. > May be we can pass arch_scale_freq_capacity value instead of max one > as a parameter of update_util function prototype No, since its a compile time thing, we can simply do: #ifdef arch_scale_freq_capacity next_freq = (1 + 1/n) * max_freq * (util / max) #else next_freq = (1 + 1/n) * current_freq * (util_raw / max) #endif -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
