[ceilometer] document new cpu.delta meter and related transformer

Change-Id: I0473a023138c81a5e4e0201708b834e1957d90b6
Closes-Bug: #1498514

doc/admin-guide-cloud/source/telemetry-data-collection.rst

@@ -618,6 +618,8 @@ add a list of transformer definitions. The available transformers are:
 +-----------------------+------------------------------------+
 | Unit conversion       | unit\_conversion                   |
 +-----------------------+------------------------------------+
+| Delta                 | delta                              |
++-----------------------+------------------------------------+
 
 The publishers section contains the list of publishers, where the
 samples data should be sent after the possible transformations.
@@ -811,6 +813,20 @@ silly meter that shows average CPU time per core::
     Expression evaluation gracefully handles NaNs and exceptions. In
     such a case it does not create a new sample but only logs a warning.
 
+**Delta transformer**
+
+This transformer calculates the change between two sample datapoints of a
+resource. It can be configured to capture only the positive growth deltas.
+
+Example configuration::
+
+    transformers:
+        - name: "delta"
+          parameters:
+            target:
+                name: "cpu.delta"
+            growth_only: True
+
 .. _telemetry-meter-definitions:
 
 Meter definitions

doc/admin-guide-cloud/source/telemetry-measurements.rst

@@ -350,6 +350,12 @@ The following meters are collected for OpenStack Compute:
 |           |       |      |          | Pollster | vSphere,| (OpenStack types)|
 |           |       |      |          |          | XenAPI  |                  |
 +-----------+-------+------+----------+----------+---------+------------------+
+| **Meters added in the Liberty release**                                     |
++-----------+-------+------+----------+----------+---------+------------------+
+| cpu.delta | Delta | ns   | instance | Pollster | Libvirt,| CPU time used s\ |
+|           |       |      | ID       |          | Hyper-V | ince previous d\ |
+|           |       |      |          |          |         | atapoint         |
++-----------+-------+------+----------+----------+---------+------------------+
 
 |