On 03-Jul 14:38, Douglas Raillard wrote: > Hi Peter, > > On 7/2/19 4:44 PM, Peter Zijlstra wrote: > > On Thu, Jun 27, 2019 at 06:15:58PM +0100, Douglas RAILLARD wrote: > > > Make schedutil cpufreq governor energy-aware. > > > > > > - patch 1 introduces a function to retrieve a frequency given a base > > > frequency and an energy cost margin. > > > - patch 2 links Energy Model perf_domain to sugov_policy. > > > - patch 3 updates get_next_freq() to make use of the Energy Model. > > > > > > > > 1) Selecting the highest possible frequency for a given cost. Some > > > platforms can have lower frequencies that are less efficient than > > > higher ones, in which case they should be skipped for most purposes. > > > They can still be useful to give more freedom to thermal throttling > > > mechanisms, but not under normal circumstances. > > > note: the EM framework will warn about such OPPs "hertz/watts ratio > > > non-monotonically decreasing" > > > > Humm, for some reason I was thinking we explicitly skipped those OPPs > > and they already weren't used. > > > > This isn't in fact so, and these first few patches make it so? > > That's correct, the cost information about each OPP has been introduced > recently in mainline > by the energy model series. Without that info, the only way to skip them that > comes to my > mind is to set a policy min frequency, since these inefficient OPPs are > usually located > at the lower end.
Perhaps it's also worth to point out that the alternative approach you point out above is a system wide solution. While, the ramp_boost thingy you propose, it's a more fine grained mechanisms which could be extended in the future to have a per-task side. IOW, it could contribute to have better user-space hints, for example to ramp_boost more certain tasks and not others. Best, Patrick -- #include <best/regards.h> Patrick Bellasi
