Add basic documentation on Performance Meters

include/performance-meters.html

@@ -0,0 +1,17 @@
+<p>
+	The <dfn>Performance Meters</dfn> window provides low-level metering
+	of the digital signal processing taking place inside Ardour.
+	One of the scenarios where this is useful is when you need to determine
+	whether Ardour is in charge for excessive xruns.
+</p>
+
+<figure class=center>
+<img src="/images/performance-meters.png" alt="The Performance Meters window" width="50%" />
+<figcaption class=center>The Performance Meters window</figcaption>
+</figure>
+
+<p>
+	This window displays worst case scenario measurements that do not necessarily match the DSP meter in the top right corner of the window. To see average
+	and standard deviation values, hover either the Engine or the Session values
+	with the mouse pointer to see the tooltip.
+</p>

master-doc.txt

@@ -2061,6 +2061,15 @@ uri: troubleshooting/plugin-dsp-load
 part: chapter
 ---
 
+---
+title: Performance Meters
+menu_title: Performance Meters
+include: performance-meters.html
+link: performance-meters
+uri: troubleshooting/performance-meters
+part: chapter
+---
+
 ---
 title: Scripting
 part: part