Messages in this thread Patch in this message | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v2] schedutil: Allow cpufreq requests to be made even when kthread kicked | Date | Tue, 22 May 2018 14:22:20 +0200 |
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On Tuesday, May 22, 2018 1:42:05 PM CEST Rafael J. Wysocki wrote: > On Tue, May 22, 2018 at 1:38 PM, Viresh Kumar <viresh.kumar@linaro.org> wrote: > > On 22-05-18, 13:31, Rafael J. Wysocki wrote: > >> So below is my (compiled-only) version of the $subject patch, obviously based > >> on the Joel's work. > >> > >> Roughly, what it does is to move the fast_switch_enabled path entirely to > >> sugov_update_single() and take the spinlock around sugov_update_commit() > >> in the one-CPU case too.
[cut]
> > > > Why do you assume that fast switch isn't possible in shared policy > > cases ? It infact is already enabled for few drivers.
I hope that fast_switch is not used with devfs_possible_from_any_cpu set in the one-CPU policy case, as that looks racy even without any patching.
> OK, so the fast_switch thing needs to be left outside of the spinlock > in the single case only. Fair enough.
That would be something like the patch below (again, compiled-only).
--- kernel/sched/cpufreq_schedutil.c | 67 +++++++++++++++++++++++++++------------ 1 file changed, 47 insertions(+), 20 deletions(-)
Index: linux-pm/kernel/sched/cpufreq_schedutil.c =================================================================== --- linux-pm.orig/kernel/sched/cpufreq_schedutil.c +++ linux-pm/kernel/sched/cpufreq_schedutil.c @@ -92,9 +92,6 @@ static bool sugov_should_update_freq(str !cpufreq_can_do_remote_dvfs(sg_policy->policy)) return false; - if (sg_policy->work_in_progress) - return false; - if (unlikely(sg_policy->need_freq_update)) return true; @@ -103,25 +100,41 @@ static bool sugov_should_update_freq(str return delta_ns >= sg_policy->freq_update_delay_ns; } -static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time, - unsigned int next_freq) +static bool sugov_update_next_freq(struct sugov_policy *sg_policy, u64 time, + unsigned int next_freq) { - struct cpufreq_policy *policy = sg_policy->policy; - if (sg_policy->next_freq == next_freq) - return; + return false; sg_policy->next_freq = next_freq; sg_policy->last_freq_update_time = time; - if (policy->fast_switch_enabled) { - next_freq = cpufreq_driver_fast_switch(policy, next_freq); - if (!next_freq) - return; + return true; +} - policy->cur = next_freq; - trace_cpu_frequency(next_freq, smp_processor_id()); - } else { +static void sugov_fast_switch(struct sugov_policy *sg_policy, u64 time, + unsigned int next_freq) +{ + struct cpufreq_policy *policy = sg_policy->policy; + + if (!sugov_update_next_freq(sg_policy, time, next_freq)) + return; + + next_freq = cpufreq_driver_fast_switch(policy, next_freq); + if (!next_freq) + return; + + policy->cur = next_freq; + trace_cpu_frequency(next_freq, smp_processor_id()); +} + +static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time, + unsigned int next_freq) +{ + if (!sugov_update_next_freq(sg_policy, time, next_freq)) + return; + + if (!sg_policy->work_in_progress) { sg_policy->work_in_progress = true; irq_work_queue(&sg_policy->irq_work); } @@ -307,7 +320,13 @@ static void sugov_update_single(struct u sg_policy->cached_raw_freq = 0; } - sugov_update_commit(sg_policy, time, next_f); + if (sg_policy->policy->fast_switch_enabled) { + sugov_fast_switch(sg_policy, time, next_f); + } else { + raw_spin_lock(&sg_policy->update_lock); + sugov_update_commit(sg_policy, time, next_f); + raw_spin_unlock(&sg_policy->update_lock); + } } static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) @@ -367,7 +386,10 @@ sugov_update_shared(struct update_util_d if (sugov_should_update_freq(sg_policy, time)) { next_f = sugov_next_freq_shared(sg_cpu, time); - sugov_update_commit(sg_policy, time, next_f); + if (sg_policy->policy->fast_switch_enabled) + sugov_fast_switch(sg_policy, time, next_f); + else + sugov_update_commit(sg_policy, time, next_f); } raw_spin_unlock(&sg_policy->update_lock); @@ -376,13 +398,18 @@ sugov_update_shared(struct update_util_d static void sugov_work(struct kthread_work *work) { struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work); + unsigned int next_freq; + unsigned long flags; + + raw_spin_lock_irqsave(&sg_policy->update_lock, flags); + next_freq = sg_policy->next_freq; + sg_policy->work_in_progress = false; + raw_spin_unlock_irqrestore(&sg_policy->update_lock, flags); mutex_lock(&sg_policy->work_lock); - __cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq, + __cpufreq_driver_target(sg_policy->policy, next_freq, CPUFREQ_RELATION_L); mutex_unlock(&sg_policy->work_lock); - - sg_policy->work_in_progress = false; } static void sugov_irq_work(struct irq_work *irq_work)
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