summaryrefslogtreecommitdiffstats
path: root/Documentation/scheduler/sched-energy.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/scheduler/sched-energy.rst')
-rw-r--r--Documentation/scheduler/sched-energy.rst29
1 files changed, 3 insertions, 26 deletions
diff --git a/Documentation/scheduler/sched-energy.rst b/Documentation/scheduler/sched-energy.rst
index fc853c8cc3..70e2921ef7 100644
--- a/Documentation/scheduler/sched-energy.rst
+++ b/Documentation/scheduler/sched-energy.rst
@@ -359,32 +359,9 @@ in milli-Watts or in an 'abstract scale'.
6.3 - Energy Model complexity
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-The task wake-up path is very latency-sensitive. When the EM of a platform is
-too complex (too many CPUs, too many performance domains, too many performance
-states, ...), the cost of using it in the wake-up path can become prohibitive.
-The energy-aware wake-up algorithm has a complexity of:
-
- C = Nd * (Nc + Ns)
-
-with: Nd the number of performance domains; Nc the number of CPUs; and Ns the
-total number of OPPs (ex: for two perf. domains with 4 OPPs each, Ns = 8).
-
-A complexity check is performed at the root domain level, when scheduling
-domains are built. EAS will not start on a root domain if its C happens to be
-higher than the completely arbitrary EM_MAX_COMPLEXITY threshold (2048 at the
-time of writing).
-
-If you really want to use EAS but the complexity of your platform's Energy
-Model is too high to be used with a single root domain, you're left with only
-two possible options:
-
- 1. split your system into separate, smaller, root domains using exclusive
- cpusets and enable EAS locally on each of them. This option has the
- benefit to work out of the box but the drawback of preventing load
- balance between root domains, which can result in an unbalanced system
- overall;
- 2. submit patches to reduce the complexity of the EAS wake-up algorithm,
- hence enabling it to cope with larger EMs in reasonable time.
+EAS does not impose any complexity limit on the number of PDs/OPPs/CPUs but
+restricts the number of CPUs to EM_MAX_NUM_CPUS to prevent overflows during
+the energy estimation.
6.4 - Schedutil governor