cpufreq: governors: Calculate iowait time only when necessary

Currently we always calculate the CPU iowait time and add it to idle time.
If we are in ondemand and we use io_is_busy, we re-calculate iowait time
and we subtract it from idle time.

With this patch iowait time is calculated only when necessary avoiding
the double call to get_cpu_iowait_time_us. We use a parameter in
function get_cpu_idle_time to distinguish when the iowait time will be
added to idle time or not, without the need of keeping the prev_io_wait.

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

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 459f9ee39c74..14714787b724 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -339,11 +339,20 @@ static ssize_t store_io_is_busy(struct dbs_data *dbs_data, const char *buf,
         struct od_dbs_tuners *od_tuners = dbs_data->tuners;
         unsigned int input;
         int ret;
+        unsigned int j;
 
         ret = sscanf(buf, "%u", &input);
         if (ret != 1)
                 return -EINVAL;
         od_tuners->io_is_busy = !!input;
+
+        /* we need to re-evaluate prev_cpu_idle */
+        for_each_online_cpu(j) {
+                struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
+                                                                        j);
+                dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
+                        &dbs_info->cdbs.prev_cpu_wall, od_tuners->io_is_busy);
+        }
         return count;
 }
 
@@ -414,7 +423,7 @@ static ssize_t store_ignore_nice(struct dbs_data *dbs_data, const char *buf,
                 struct od_cpu_dbs_info_s *dbs_info;
                 dbs_info = &per_cpu(od_cpu_dbs_info, j);
                 dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
-                                                &dbs_info->cdbs.prev_cpu_wall);
+                        &dbs_info->cdbs.prev_cpu_wall, od_tuners->io_is_busy);
                 if (od_tuners->ignore_nice)
                         dbs_info->cdbs.prev_cpu_nice =
                                 kcpustat_cpu(j).cpustat[CPUTIME_NICE];