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    SubjectRe: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits
    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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