On 06/03/2013 02:24 PM, Viresh Kumar wrote: > On 3 June 2013 16:27, Rafael J. Wysocki <rjw@xxxxxxx> wrote: >> The question is if we want policy->max to re-scale them effectively (i.e. to >> change weights so that the maximum load maps to the highest frequency available >> at the moment) or if we want policy->max to work as a cap (i.e. to map all >> loads above certain value to the maximum frequency available at the moment, so >> that the criteria for selecting the lower frequencies don't change). In my >> opinion the second option is better, because it means "OK, we can't use some >> high frequencies, but let's not hurt performance for the loads that wouldn't >> require them anyway". Otherwise, we'll effectively throttle all loads and >> that not only causes performance to drop, but also causes more energy to be >> used overall. > > I wouldn't say that I don't agree with you as I do to some extent. > > But the question that comes to my mind now is: Why is policy->max reduced > in the first place? User doesn't have control over which freqs to expose, so > available_frequencies will stay the same. The only thing he is capable > of doing is: reduce policy->max.. Which in a way means that.. "I don't want to > use higher frequencies (power, thermal reasons) and I know performance will > go down with it and I don't care for it now." > > And this way I feel policy->max isn't a bad choice either. > > BUT as you said: policy->max isn't there to say don't be so aggressive now in > increasing frequencies but just only to say, don't go over this frequency.. > > So, probably we can use cpuinfo.max_freq :) > Both of you know better than me, but I also believe that cpuinfo.max is more appropriate. Although, the decision was taken, let me share a spreadsheet to show the 2 cases. https://docs.google.com/spreadsheet/ccc?key=0AnMfNYUV1k0ddHh1OUFXa0kxcGZJaXd4am1sdmVWT0E&usp=sharing I will prepare the v2 of this patch that uses cpuinfo.max_freq instead of policy-max. Also, I will split the patch into 3 parts as suggested. Thank you for your comments and suggestions! Stratos -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
