Author: Carl Friedrich Bolz <cfb...@gmx.de>
Branch: extradoc
Changeset: r4846:cfdba0fcd517
Date: 2012-10-11 14:07 +0200
http://bitbucket.org/pypy/extradoc/changeset/cfdba0fcd517/
Log: fill the slides with a first rough draft
diff --git a/talk/vmil2012/presentation/talk.tex
b/talk/vmil2012/presentation/talk.tex
--- a/talk/vmil2012/presentation/talk.tex
+++ b/talk/vmil2012/presentation/talk.tex
@@ -90,6 +90,7 @@
\begin{itemize}
\item for interesting, commonly executed code paths
\item produces a linear list of operations (trace)
+ \item automatically does (potentially deep) inlining
\end{itemize}
\item trace is optimized and then turned into machine code
\end{itemize}
@@ -97,7 +98,19 @@
\begin{frame}
\frametitle{Guards}
-
+ \begin{itemize}
+ \item Points of control flow divergence are marked with guards
+ \item Operations that check whether conditions are still true
+ \item When a guard fails, execution of the trace stops and continues in
the interpreter
+ \pause
+ \begin{block}{Guard Characteristics}
+ \begin{itemize}
+ \item lots of them, up to 20\% guards
+ \item most never fail
+ \item costly to implement
+ \end{itemize}
+ \end{block}
+ \end{itemize}
\end{frame}
% this talk wants to go over a lot of details that are usually glossed over as
@@ -105,10 +118,21 @@
\begin{frame}
\frametitle{Bridges}
+ \begin{itemize}
+ \item When a trace fails often, it becomes worth to attach a new trace
to it
+ \item This is called a bridge
+ \item The bridge is attached by patching the guard machine code
+ \item when this guard fails in the future, the new trace is executed
instead
+ \end{itemize}
\end{frame}
\begin{frame}
\frametitle{RPython and PyPy}
+ \begin{itemize}
+ \item Context: RPython
+ \item a generic tracing JIT, applicable to many languages
+ \item main use: PyPy, an efficient Python interpreter
+ \end{itemize}
\end{frame}
\begin{frame}
@@ -119,14 +143,38 @@
\begin{frame}
\frametitle{Symbolic Frame Capturing}
+ \begin{itemize}
+ \item Guard can fail deep inside inlined function
+ \item when going back to the interpreter, call stack needs to be
re-created
+ \item done with the help of symbolic frame stacks
+ \item these show how trace trace variables fill the to-be-built stack
frames
+ \end{itemize}
\end{frame}
\begin{frame}
\frametitle{Symbolic Frame Compression}
+ \begin{itemize}
+ \item There are \emph{a lot of} guards
+ \item Naively storing symbolic frames would be costly in terms of memory
+ \item need to store them compactly
+ \item observation: from one guard to the next, the non-top stack frames
don't change
+ \item share these between subsequent guards
+ \pause
+ \item also need a byte-saving binary representation, but that's just
boring work
+ \end{itemize}
\end{frame}
\begin{frame}
\frametitle{Interaction with Optimization}
+ \begin{itemize}
+ \item Some optimizations make it necessary to store extra information in
symbolic frames
+ \item examples:
+ \begin{itemize}
+ \item delayed heap stores (need to do stores before resuming
interpreter)
+ \item allocation remvoal (need to allocate objects before
resuming)
+ \end{itemize}
+ \item can be compressed using similar techniques
+ \end{itemize}
\end{frame}
\begin{frame}
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