[PATCH] doc/power: add info on scale mode reaction time

[David Hunt <david.hunt@intel.com>]

When using PMD Power Management, scale mode reacts slower than
monitor mode and pause mode. Add note in user guide to this
effect.

Signed-off-by: David Hunt <david.hunt@intel.com>
---
 doc/guides/prog_guide/power_man.rst               | 4 +++-
 doc/guides/sample_app_ug/l3_forward_power_man.rst | 5 +++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/doc/guides/prog_guide/power_man.rst b/doc/guides/prog_guide/power_man.rst
index e387d7811e..66592cf22f 100644
--- a/doc/guides/prog_guide/power_man.rst
+++ b/doc/guides/prog_guide/power_man.rst
@@ -216,7 +216,9 @@ power saving whenever empty poll count reaches a certain number.
 
 * Frequency scaling
    This power saving scheme will use ``librte_power`` library functionality to
-   scale the core frequency up/down depending on traffic volume.
+   scale the core frequency up/down depending on traffic volume. The reaction
+   time of the frequency scaling mode is longer than the pause and monitor
+   mode.
 
 The "monitor" mode is only supported in the following configurations and scenarios:
 
diff --git a/doc/guides/sample_app_ug/l3_forward_power_man.rst b/doc/guides/sample_app_ug/l3_forward_power_man.rst
index 8817eaadbf..84b014fab5 100644
--- a/doc/guides/sample_app_ug/l3_forward_power_man.rst
+++ b/doc/guides/sample_app_ug/l3_forward_power_man.rst
@@ -345,8 +345,9 @@ and has three available power management schemes:
   to avoid busy looping when there is no traffic.
 
 ``scale``
-  This will use frequency scaling routines
-  available in the ``librte_power`` library.
+  This will use frequency scaling routines available in
+  the ``librte_power`` library. The reaction time of the
+  scale mode is longer than the pause and monitor mode.
 
 See :doc:`Power Management<../prog_guide/power_man>` chapter
 in the DPDK Programmer's Guide for more details on PMD power management.
-- 
2.17.1