Messages in this thread | | | Date | Mon, 21 Nov 2016 12:12:43 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits |
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On Mon, Nov 21, 2016 at 04:18:00PM +0530, Viresh Kumar wrote: > On 21-11-16, 11:19, Peter Zijlstra wrote: > > Urgh... > > > > > > So no tunables and rate limits here at all please. > > > > During LPC we discussed the rampup and decay issues and decided that we > > should very much first address them by playing with the PELT stuff. > > Morton was going to play with capping the decay on the util signal. This > > should greatly improve the ramp-up scenario and cure some other wobbles. > > > > The decay can be set by changing the over-all pelt decay, if so desired. > > > > Also, there was the idea of; once the above ideas have all been > > explored; tying the freq ram rate to the power curve. > > > > So NAK on everything tunable here. > > Okay, as I told you on IRC, we already have a tunable: rate_limit_us for the > schedutil governor which defines the minimum time before which the governor > wouldn't try to update the frequency again. Perhaps 10-20 ms is the ideal value > for that everyone is using. > > So eventually that should also die and we should get inputs from PELT stuff ?
I think it should be replaced by a value provided by the driver. It makes sense to have a rate-limit in so far as that it doesn't make sense to try and program the hardware faster than it can actually change frequencies and/or have a programming cost amortization. And this very clearly is a driver specific thing.
It however doesn't make sense to me to fudge with this in order to achieve ramp up/down differences.
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