wl12xx: adaptive sched scan dwell times

[cascardo/linux.git] / drivers / cpufreq / cpufreq_ondemand.c

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index c3e0652..836e9b0 100644 (file)
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -257,6 +257,62 @@ show_one(sampling_down_factor, sampling_down_factor);
 show_one(ignore_nice_load, ignore_nice);
 show_one(powersave_bias, powersave_bias);
 
+/**
+ * update_sampling_rate - update sampling rate effective immediately if needed.
+ * @new_rate: new sampling rate
+ *
+ * If new rate is smaller than the old, simply updaing
+ * dbs_tuners_int.sampling_rate might not be appropriate. For example,
+ * if the original sampling_rate was 1 second and the requested new sampling
+ * rate is 10 ms because the user needs immediate reaction from ondemand
+ * governor, but not sure if higher frequency will be required or not,
+ * then, the governor may change the sampling rate too late; up to 1 second
+ * later. Thus, if we are reducing the sampling rate, we need to make the
+ * new value effective immediately.
+ */
+static void update_sampling_rate(unsigned int new_rate)
+{
+       int cpu;
+
+       dbs_tuners_ins.sampling_rate = new_rate
+                                    = max(new_rate, min_sampling_rate);
+
+       for_each_online_cpu(cpu) {
+               struct cpufreq_policy *policy;
+               struct cpu_dbs_info_s *dbs_info;
+               unsigned long next_sampling, appointed_at;
+
+               policy = cpufreq_cpu_get(cpu);
+               if (!policy)
+                       continue;
+               dbs_info = &per_cpu(od_cpu_dbs_info, policy->cpu);
+               cpufreq_cpu_put(policy);
+
+               mutex_lock(&dbs_info->timer_mutex);
+
+               if (!delayed_work_pending(&dbs_info->work)) {
+                       mutex_unlock(&dbs_info->timer_mutex);
+                       continue;
+               }
+
+               next_sampling  = jiffies + usecs_to_jiffies(new_rate);
+               appointed_at = dbs_info->work.timer.expires;
+
+
+               if (time_before(next_sampling, appointed_at)) {
+
+                       mutex_unlock(&dbs_info->timer_mutex);
+                       cancel_delayed_work_sync(&dbs_info->work);
+                       mutex_lock(&dbs_info->timer_mutex);
+
+                       schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work,
+                                                usecs_to_jiffies(new_rate));
+
+               }
+               mutex_unlock(&dbs_info->timer_mutex);
+       }
+}
+
 static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
                                   const char *buf, size_t count)
 {
@@ -265,7 +321,7 @@ static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
        ret = sscanf(buf, "%u", &input);
        if (ret != 1)
                return -EINVAL;
-       dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
+       update_sampling_rate(input);
        return count;
 }