Documentation: intel_pstate: Describe hwp_dynamic_boost sysfs knob

Document the recently introduced hwp_dynamic_boost sysfs knob allowing user space to tell intel_pstate to use iowait boosting in the active mode with HWP enabled (to improve performance). Signed-off-by: Rafael J. Wysocki <[email protected]> Acked-by: Srinivas Pandruvada <[email protected]>
olifre · Jun 27, 2018 · 649f53a · 649f53a
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diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst
@@ -378,6 +378,17 @@ argument is passed to the kernel in the command line.
 	but it affects the maximum possible value of per-policy P-state	limits
 	(see `Interpretation of Policy Attributes`_ below for details).
 
+``hwp_dynamic_boost``
+	This attribute is only present if ``intel_pstate`` works in the
+	`active mode with the HWP feature enabled <Active Mode With HWP_>`_ in
+	the processor.  If set (equal to 1), it causes the minimum P-state limit
+	to be increased dynamically for a short time whenever a task previously
+	waiting on I/O is selected to run on a given logical CPU (the purpose
+	of this mechanism is to improve performance).
+
+	This setting has no effect on logical CPUs whose minimum P-state limit
+	is directly set to the highest non-turbo P-state or above it.
+
 .. _status_attr:
 
 ``status``