Hi Rafael, On 11/04/17 23:23, Rafael J. Wysocki wrote: > On Thu, Mar 30, 2017 at 11:36 PM, Rafael J. Wysocki <[email protected]> > wrote: > > From: Rafael J. Wysocki <[email protected]> > > > > The schedutil governor reduces frequencies too fast in some > > situations which cases undesirable performance drops to > > appear. > > > > To address that issue, make schedutil reduce the frequency slower by > > setting it to the average of the value chosen during the previous > > iteration of governor computations and the new one coming from its > > frequency selection formula. > > > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=194963 > > Reported-by: John <[email protected]> > > Signed-off-by: Rafael J. Wysocki <[email protected]> > > --- > > > > This addresses a practical issue, but one in the "responsiveness" or > > "interactivity" category which is quite hard to represent quantitatively. > > > > As reported by John in BZ194963, schedutil does not ramp up P-states quickly > > enough which causes audio issues to appear in his gaming setup. At least it > > evidently is worse than ondemand in this respect and the patch below helps. > > > > The patch essentially repeats the trick added some time ago to the > > load-based > > P-state selection algorithm in intel_pstate, which allowed us to make it > > viable > > for performance-oriented users, and which is to reduce frequencies at a > > slower > > pace. > > > > The reason why I chose the average is because it is computationally cheap > > and pretty much the max reasonable slowdown and the idea is that in case > > there's something about to run that we don't know about yet, it is better to > > stay at a higher level for a while more to avoid having to get up from the > > floor > > every time. > > > > But technically speaking it is a filter. :-) > > > > So among other things I'm wondering if that leads to substantial increases > > in > > energy consumption anywhere. > > I haven't seen any numbers indicating that, so since the issue > addressed by this patch is real, I'd like to go ahead with it for > 4.12. >
Sorry, it took a bit of time to get results. I didn't see big power/perf regressions on interactive type of workloads running on Pixel phones. Youtube only showed a +~2% energy increase, but I can't say for certain that is not in the noise. My experiments also have your other two patches [1] applied. So, yeah. I guess we could go ahead with this and see if we can improve further in the future. Thanks, - Juri [1] https://marc.info/?l=linux-kernel&m=149178351728004&w=2
