On Tuesday, May 22, 2018 12:54:29 PM CEST Viresh Kumar wrote: > On 22-05-18, 12:50, Rafael J. Wysocki wrote: > > Ugly indeed. > > Hehe. I was thinking, maybe we can write wrapper helpers around lock/unlock > which are stored as pointers in sg_policy. So that those are only set to > non-NULL values (or non-Noop routines) for slow-switching single policy or > any-switching shared policy systems. Then we can get rid of such conditional > locking attempts :) > >
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. --- kernel/sched/cpufreq_schedutil.c | 57 ++++++++++++++++++++++++++------------- 1 file changed, 38 insertions(+), 19 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 +100,25 @@ 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_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); } @@ -277,6 +274,7 @@ static void sugov_update_single(struct u { struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util); struct sugov_policy *sg_policy = sg_cpu->sg_policy; + struct cpufreq_policy *policy = sg_policy->policy; unsigned long util, max; unsigned int next_f; bool busy; @@ -307,7 +305,23 @@ static void sugov_update_single(struct u sg_policy->cached_raw_freq = 0; } - sugov_update_commit(sg_policy, time, next_f); + if (policy->fast_switch_enabled) { + if (!sugov_update_next_freq(sg_policy, time, next_f)) + return; + + next_f = cpufreq_driver_fast_switch(policy, next_f); + if (!next_f) + return; + + policy->cur = next_f; + trace_cpu_frequency(next_f, smp_processor_id()); + } 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) @@ -376,13 +390,18 @@ 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)