debugging: slides: reword flamegraphs interpretation slide

Signed-off-by: Alexis Lothoré <[email protected]>

Author: Tropicao

slides/debugging-system-wide-profiling/debugging-system-wide-profiling.tex

@@ -415,7 +415,7 @@ \subsection{perf}
 \end{frame} 
 
 \begin{frame}[fragile]
-  \frametitle{Visualizing data with flamegraphs (1/2)}
+  \frametitle{Visualizing data with flamegraphs}
   \begin{itemize}
     \item Get the flamegraph scripts:
   \begin{block}{}
@@ -453,17 +453,19 @@ \subsection{perf}
 \end{frame}
 
 \begin{frame}[fragile]
-  \frametitle{Visualizing data with flamegraphs (2/2)}
+  \frametitle{Flamegraph example: CPU flamegraph}
   \center
 	\includegraphics[width=1.0\textwidth]{slides/debugging-system-wide-profiling/flamegraph.png}\\
   \begin{itemize}
+    \item The plates on top represent the functions sampled by perf during
+      the recording
     \item The plates width represents how often a function has been
-      sampled
-    \item The "spikes" height represents the call stacks depth
-    \item Flamegraphs are interactive: clicking a plate will put focus on the
+      sampled by perf
+    \item The plates below represent the call stacks for the sampled functions
+    \item Flamegraphs are interactive: clicking on a plate will zoom on the
       corresponding callstack
-    \item Colors can be tuned at flamegraph generation, for example to have
-      a clear split between kernel and userspace functions
+    \item Colors can be tuned at flamegraph generation (eg: to get a clear
+      split between kernel and userspace)
   \end{itemize}
 \end{frame}