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SubjectRe: [PATCH V2 2/2] cpufreq: schedutil: Always process remote callback with slow switching
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On Monday, August 14, 2017 11:20:16 AM CEST Viresh Kumar wrote:
> The frequency update from the utilization update handlers can be divided
> into two parts:
>
> (A) Finding the next frequency
> (B) Updating the frequency
>
> While any CPU can do (A), (B) can be restricted to a group of CPUs only,
> depending on the current platform.
>
> For platforms where fast cpufreq switching is possible, both (A) and (B)
> are always done from the same CPU and that CPU should be capable of
> changing the frequency of the target CPU.
>
> But for platforms where fast cpufreq switching isn't possible, after
> doing (A) we wake up a kthread which will eventually do (B). This
> kthread is already bound to the right set of CPUs, i.e. only those which
> can change the frequency of CPUs of a cpufreq policy. And so any CPU
> can actually do (A) in this case, as the frequency is updated from the
> right set of CPUs only.
>
> Check cpufreq_can_do_remote_dvfs() only for the fast switching case.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
> V2: s/policy/sg_policy->policy/, missed updating the commit with local
> updates earlier, noticed that just now.
>
> kernel/sched/cpufreq_schedutil.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 504d0752f8f2..9209d83ecdcf 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -84,13 +84,18 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
> *
> * However, drivers cannot in general deal with cross-cpu
> * requests, so while get_next_freq() will work, our
> - * sugov_update_commit() call may not.
> + * sugov_update_commit() call may not for the fast switching platforms.
> *
> * Hence stop here for remote requests if they aren't supported
> * by the hardware, as calculating the frequency is pointless if
> * we cannot in fact act on it.
> + *
> + * For the slow switching platforms, the kthread is always scheduled on
> + * the right set of CPUs and any CPU can find the next frequency and
> + * schedule the kthread.
> */
> - if (!cpufreq_can_do_remote_dvfs(sg_policy->policy))
> + if (sg_policy->policy->fast_switch_enabled &&
> + !cpufreq_can_do_remote_dvfs(sg_policy->policy))
> return false;
>
> if (sg_policy->work_in_progress)
>

Applied, thanks!


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