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    SubjectRe: [PATCH RFC v5] cpufreq: schedutil: Make iowait boost more energy efficient
    On 18-07-17, 15:02, Juri Lelli wrote:
    > Mmm, seems to make sense to me. :/
    >
    > Would the following work (on top of Joel's v5)? Rationale being that
    > only in sugov_set_iowait_boost we might bump freq up (if no iowait_boost
    > was set) or start from policy->min. In sugov_iowait_boost (consumer)
    > instead we do the decay (if no boosting was pending).
    >
    > ---
    > kernel/sched/cpufreq_schedutil.c | 29 +++++++++++++++++++----------
    > 1 file changed, 19 insertions(+), 10 deletions(-)
    >
    > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
    > index 46b2479641cc..b270563c15a5 100644
    > --- a/kernel/sched/cpufreq_schedutil.c
    > +++ b/kernel/sched/cpufreq_schedutil.c
    > @@ -171,8 +171,14 @@ static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
    > {
    > if (flags & SCHED_CPUFREQ_IOWAIT) {
    > sg_cpu->iowait_boost_pending = true;
    > - sg_cpu->iowait_boost = max(sg_cpu->iowait_boost,
    > - sg_cpu->sg_policy->policy->min);
    > + if (sg_cpu->iowait_boost) {
    > + /* Bump up 2*current_boost until hitting max */
    > + sg_cpu->iowait_boost = max(sg_cpu->iowait_boost << 1,
    > + sg_cpu->iowait_boost_max);

    And we are back at where we started :)

    This wouldn't work because sugov_set_iowait_boost() gets called a lot.
    Maybe 10 times within a rate_limit_us period.

    The thumb rule is, never double/half the boost from
    sugov_set_iowait_boost() :)

    --
    viresh

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