cpufreq: ondemand: update update_sampling_rate() to make it more efficient

Currently update_sampling_rate() runs over each online CPU and
cancels/queues timers on all policy->cpus every time. This should be
done just once for any cpu belonging to a policy.

Create a cpumask and keep on clearing it as and when we process
policies, so that we don't have to traverse through all CPUs of the same
policy.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index f879012cf849959ed8a7eaad9b92a93316fc90be..eae51070c03427573708fe2bd67a081ccc2ffe82 100644 (file)
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -246,6 +246,7 @@ static void update_sampling_rate(struct dbs_data *dbs_data,
                unsigned int new_rate)
 {
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
+       struct cpumask cpumask;
        int cpu;
 
        od_tuners->sampling_rate = new_rate = max(new_rate,
@@ -256,7 +257,9 @@ static void update_sampling_rate(struct dbs_data *dbs_data,
         */
        mutex_lock(&od_dbs_cdata.mutex);
 
-       for_each_online_cpu(cpu) {
+       cpumask_copy(&cpumask, cpu_online_mask);
+
+       for_each_cpu(cpu, &cpumask) {
                struct cpufreq_policy *policy;
                struct od_cpu_dbs_info_s *dbs_info;
                struct cpu_dbs_info *cdbs;
@@ -276,6 +279,9 @@ static void update_sampling_rate(struct dbs_data *dbs_data,
 
                policy = shared->policy;
 
+               /* clear all CPUs of this policy */
+               cpumask_andnot(&cpumask, &cpumask, policy->cpus);
+
                /*
                 * Update sampling rate for CPUs whose policy is governed by
                 * dbs_data. In case of governor_per_policy, only a single
@@ -285,6 +291,10 @@ static void update_sampling_rate(struct dbs_data *dbs_data,
                if (dbs_data != policy->governor_data)
                        continue;
 
+               /*
+                * Checking this for any CPU should be fine, timers for all of
+                * them are scheduled together.
+                */
                next_sampling = jiffies + usecs_to_jiffies(new_rate);
                appointed_at = dbs_info->cdbs.timer.expires;