Documentation: intel_pstate: Clarify coordination of P-State limits

spandruvada · rafaeljw · commit 60935c17e26a · 2018-11-29T22:31:58.000+01:00
Explain influence of per-core P-states and hyper threading on the
effective performance.

Signed-off-by: Srinivas Pandruvada &lt;srinivas.pandruvada@linux.intel.com&gt;
Signed-off-by: Rafael J. Wysocki &lt;rafael.j.wysocki@intel.com&gt;
diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst
@@ -495,7 +495,15 @@ on the following rules, regardless of the current operation mode of the driver:
 
  2. Each individual CPU is affected by its own per-policy limits (that is, it
     cannot be requested to run faster than its own per-policy maximum and it
-    cannot be requested to run slower than its own per-policy minimum).
+    cannot be requested to run slower than its own per-policy minimum). The
+    effective performance depends on whether the platform supports per core
+    P-states, hyper-threading is enabled and on current performance requests
+    from other CPUs. When platform doesn't support per core P-states, the
+    effective performance can be more than the policy limits set on a CPU, if
+    other CPUs are requesting higher performance at that moment. Even with per
+    core P-states support, when hyper-threading is enabled, if the sibling CPU
+    is requesting higher performance, the other siblings will get higher
+    performance than their policy limits.
 
  3. The global and per-policy limits can be set independently.
 
