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slides/slides.tex

@@ -280,11 +280,63 @@ unwind_context_t _eh_elf(
 \section{Benchmarking}
 
 \begin{frame}{Benchmarking requirements}
-    \todo{}
+    \begin{enumerate}
+        \item Thousands of samples (single unwind: $10\,\mu{}s$)
+        \item Interesting enough program to unwind: nested functions, complex
+            FDEs
+        \item Mitigate caching: don't always unwind from the \emph{same} point
+        \item Yet be fair: don't always unwind from totally different places
+        \item Distribute evenly: if possible, also from within libraries
+    \end{enumerate}
+
+    \pause{}\vspace{1em}
+
+    \begin{itemize}
+        \item 2 $\implies$ exit hand-crafted program, exit CSmith
+        \item 5 $\implies$ cannot call the unwinding procedure by hand
+    \end{itemize}
 \end{frame}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\subsection{}
+\subsection{Unwinding using perf}
+
+\begin{frame}{Presentation of perf}
+    \textbf{A profiler is used to\ldots}
+    \begin{itemize}
+        \item get readings of the \alert{time spent in each function}
+        \item detect ``hot paths'': functions you ought to optimize
+        \item \ldots{}and \alert{benchmark \ehelfs{}}!
+    \end{itemize}
+
+    \vspace{1em}\pause{}
+    \textbf{How does it work?}
+    \begin{itemize}
+        \item{} \alert{Polling profiler}: stops at regular intervals to perform
+            analyses
+        \item{} Upon polling, \alert{dumps the stack} to a file
+        \item{} In the analysis phase (after the program terminated),
+            \alert{unwinds all the stacks gathered} to get call paths
+    \end{itemize}
+\end{frame}
+
+\begin{frame}{perf instrumentation}
+    \textbf{Instrumenting perf matches all the requirements!}
+    \vspace{1em}\pause{}
+
+    \begin{itemize}
+        \item{} \alert{Plug \ehelfs{} into perf}: use \ehelfs{} instead of
+            DWARF to analyze stack dumps
+        \item{} Implement \alert{unwinding performance counters} inside perf
+            \bigskip{}
+
+        \item{} Use perf on \alert{hackbench}, a kernel stress-test program
+            \begin{itemize}
+                \item Small program
+                \item Lots of calls
+                \item Relies on libc, libpthread
+            \end{itemize}
+    \end{itemize}
+\end{frame}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{A glance at future work}