Merge branch 'perf/core' into perf/uprobes

Merge in latest upstream (and the latest perf development tree),
to prepare for tooling changes, and also to pick up v3.4 MM
changes that the uprobes code needs to take care of.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 57 insertions, 1 deletions

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index c3e0652520a..836e9b062e5 100644
--- 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;
 }