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>
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 326f0c2..443442d 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -67,13 +67,13 @@
return cputime_to_usecs(idle_time);
}
-u64 get_cpu_idle_time(unsigned int cpu, u64 *wall)
+u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy)
{
- u64 idle_time = get_cpu_idle_time_us(cpu, NULL);
+ u64 idle_time = get_cpu_idle_time_us(cpu, io_busy ? wall : NULL);
if (idle_time == -1ULL)
return get_cpu_idle_time_jiffy(cpu, wall);
- else
+ else if (!io_busy)
idle_time += get_cpu_iowait_time_us(cpu, wall);
return idle_time;
@@ -100,13 +100,22 @@
/* Get Absolute Load (in terms of freq for ondemand gov) */
for_each_cpu(j, policy->cpus) {
struct cpu_dbs_common_info *j_cdbs;
- u64 cur_wall_time, cur_idle_time, cur_iowait_time;
- unsigned int idle_time, wall_time, iowait_time;
+ u64 cur_wall_time, cur_idle_time;
+ unsigned int idle_time, wall_time;
unsigned int load;
+ int io_busy = 0;
j_cdbs = dbs_data->cdata->get_cpu_cdbs(j);
- cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);
+ /*
+ * For the purpose of ondemand, waiting for disk IO is
+ * an indication that you're performance critical, and
+ * not that the system is actually idle. So do not add
+ * the iowait time to the cpu idle time.
+ */
+ if (dbs_data->cdata->governor == GOV_ONDEMAND)
+ io_busy = od_tuners->io_is_busy;
+ cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy);
wall_time = (unsigned int)
(cur_wall_time - j_cdbs->prev_cpu_wall);
@@ -134,29 +143,6 @@
idle_time += jiffies_to_usecs(cur_nice_jiffies);
}
- if (dbs_data->cdata->governor == GOV_ONDEMAND) {
- struct od_cpu_dbs_info_s *od_j_dbs_info =
- dbs_data->cdata->get_cpu_dbs_info_s(cpu);
-
- cur_iowait_time = get_cpu_iowait_time_us(j,
- &cur_wall_time);
- if (cur_iowait_time == -1ULL)
- cur_iowait_time = 0;
-
- iowait_time = (unsigned int) (cur_iowait_time -
- od_j_dbs_info->prev_cpu_iowait);
- od_j_dbs_info->prev_cpu_iowait = cur_iowait_time;
-
- /*
- * For the purpose of ondemand, waiting for disk IO is
- * an indication that you're performance critical, and
- * not that the system is actually idle. So subtract the
- * iowait time from the cpu idle time.
- */
- if (od_tuners->io_is_busy && idle_time >= iowait_time)
- idle_time -= iowait_time;
- }
-
if (unlikely(!wall_time || wall_time < idle_time))
continue;
@@ -254,6 +240,7 @@
struct cs_dbs_tuners *cs_tuners = NULL;
struct cpu_dbs_common_info *cpu_cdbs;
unsigned int sampling_rate, latency, ignore_nice, j, cpu = policy->cpu;
+ int io_busy = 0;
int rc;
if (have_governor_per_policy())
@@ -353,6 +340,7 @@
sampling_rate = od_tuners->sampling_rate;
ignore_nice = od_tuners->ignore_nice;
od_ops = dbs_data->cdata->gov_ops;
+ io_busy = od_tuners->io_is_busy;
}
switch (event) {
@@ -369,7 +357,7 @@
j_cdbs->cpu = j;
j_cdbs->cur_policy = policy;
j_cdbs->prev_cpu_idle = get_cpu_idle_time(j,
- &j_cdbs->prev_cpu_wall);
+ &j_cdbs->prev_cpu_wall, io_busy);
if (ignore_nice)
j_cdbs->prev_cpu_nice =
kcpustat_cpu(j).cpustat[CPUTIME_NICE];