It is not worth the overhead to migrate tasks for tiny insignificant
energy savings. To prevent this, an energy margin is introduced in
energy_diff() which effectively adds a dead-zone that rounds tiny energy
differences to zero. Since no scale is enforced for energy model data
the margin can't be absolute. Instead it is defined as +/-1.56% energy
saving compared to the current total estimated energy consumption.
Change-Id: I6be069c752c701fb825430896b3b768a7ab2fee4
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
[rebase: on top of msm-google/android-msm-marlin-3.18,
massage original patch which changes code in energy_diff()
into __energy_diff() introduced by SchedTune]
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
(cherry picked from commit
780cb5a5fa47adf13d4fc2b77e8e94448cd56098)
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
struct sched_domain *sd;
struct sched_group *sg;
int sd_cpu = -1, energy_before = 0, energy_after = 0;
+ int diff, margin;
struct energy_env eenv_before = {
.util_delta = 0,
eenv->cap.before, eenv->cap.after, eenv->cap.delta,
eenv->nrg.delta, eenv->payoff);
+ /*
+ * Dead-zone margin preventing too many migrations.
+ */
+
+ margin = eenv->nrg.before >> 6; /* ~1.56% */
+
+ diff = eenv->nrg.after - eenv->nrg.before;
+
+ eenv->nrg.diff = (abs(diff) < margin) ? 0 : eenv->nrg.diff;
+
return eenv->nrg.diff;
}