Re: [PATCH v2 04/11] sched: Allow all archs to set the power_orig

From: Dietmar Eggemann
Date: Thu Jun 05 2014 - 04:59:30 EST

>> Firstly, we need to scale cpu power in update_cpu_power() regarding
>> uArch, frequency and rt/irq pressure.
>> Here the freq related value we get back from arch_scale_freq_power(...,
>> cpu) could be an instantaneous value (curr_freq(cpu)/max_freq(cpu)).
>> Secondly, to be able to scale the runnable avg sum of a sched entity
>> (se->avg->runnable_avg_sum), we preferable have a coefficient
>> representing uArch diffs (cpu_power_orig(cpu)/cpu_power_orig(most
>> powerful cpu in the system) and another coefficient (avg freq over 'now
> AFAICT, the coefficient representing uArch diffs is already taken into
> account into power_freq thanks to scale_cpu, isn't it ?

True, but I can't see how the current signature of
arch_scale_cpu_power() and arch_scale_freq_power() fit into this uArch
and freq invariant updating of se->avg->runnable_avg_sum business.

>> - sa->last_runnable_update'(cpu)/max_freq(cpu). This value would have to
>> be retrieved from the arch in __update_entity_runnable_avg().

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