cpufreq: governor: Fix CPU load information updates via ->store

The ->store() callbacks of some tunable sysfs attributes of the
ondemand and conservative governors trigger immediate updates of
the CPU load information for all CPUs "governed" by the given
dbs_data by walking the cpu_dbs_info structures for all online
CPUs in the system and updating them.

This is questionable for two reasons.  First, it may lead to a lot of
extra overhead on a system with many CPUs if the given dbs_data is
only associated with a few of them.  Second, if governor tunables are
per-policy, the CPUs associated with the other sets of governor
tunables should not be updated.

To address this issue, use the observation that in all of the places
in question the update operation may be carried out in the same way
(because all of the tunables involved are now located in struct
dbs_data and readily available to the common code) and make the
code in those places invoke the same (new) helper function that
will carry out the update correctly.

That new function always checks the ignore_nice_load tunable value
and updates the CPUs' prev_cpu_nice data fields if that's set, which
wasn't done by the original code in store_io_is_busy(), but it
should have been done in there too.

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

1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index badbd467e5e2..4b14f04daa41 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -80,6 +80,36 @@ ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
 }
 EXPORT_SYMBOL_GPL(store_sampling_rate);
 
+/**
+ * gov_update_cpu_data - Update CPU load data.
+ * @gov: Governor whose data is to be updated.
+ * @dbs_data: Top-level governor data pointer.
+ *
+ * Update CPU load data for all CPUs in the domain governed by @dbs_data
+ * (that may be a single policy or a bunch of them if governor tunables are
+ * system-wide).
+ *
+ * Call under the @dbs_data mutex.
+ */
+void gov_update_cpu_data(struct dbs_governor *gov, struct dbs_data *dbs_data)
+{
+	struct policy_dbs_info *policy_dbs;
+
+	list_for_each_entry(policy_dbs, &dbs_data->policy_dbs_list, list) {
+		unsigned int j;
+
+		for_each_cpu(j, policy_dbs->policy->cpus) {
+			struct cpu_dbs_info *j_cdbs = gov->get_cpu_cdbs(j);
+
+			j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall,
+								  dbs_data->io_is_busy);
+			if (dbs_data->ignore_nice_load)
+				j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(gov_update_cpu_data);
+
 static inline struct dbs_data *to_dbs_data(struct kobject *kobj)
 {
 	return container_of(kobj, struct dbs_data, kobj);