From dfa18101f1836fa73518971020cede43de539f7d Mon Sep 17 00:00:00 2001
From: Manuel Traut <manut@linutronix.de>
Date: Sun, 17 Oct 2010 19:08:49 +0200
Subject: mv mm-basics to kernel-devel

Signed-off-by: Manuel Traut <manut@linutronix.de>
---
 .../linux-mm-basics/pres_linux-mm-basics_en.tex    | 253 ---------------------
 1 file changed, 253 deletions(-)
 delete mode 100644 linux-basics/linux-mm-basics/pres_linux-mm-basics_en.tex

(limited to 'linux-basics/linux-mm-basics/pres_linux-mm-basics_en.tex')

diff --git a/linux-basics/linux-mm-basics/pres_linux-mm-basics_en.tex b/linux-basics/linux-mm-basics/pres_linux-mm-basics_en.tex
deleted file mode 100644
index 8ff0da7..0000000
--- a/linux-basics/linux-mm-basics/pres_linux-mm-basics_en.tex
+++ /dev/null
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-\documentclass{beamer}
-\usetheme{linutronix}
-\usepackage{german}
-\usepackage[utf8]{inputenc}
-\usepackage{pgf}
-\usepackage{graphicx}
-
-\title{Linux Memory Management basics}
-\institute{Linutronix GmbH}
-
-\begin{document}
-
-\maketitle
-\begin{frame}
-\frametitle{Overview}
-\tableofcontents
-\end{frame}
-
-\section{Basics}
-\subsection{Overview}
-\begin{frame}
-\frametitle{Overview}
-\begin{itemize}
-\item over-committing
-\item Copy-On-Write
-\item Page relocation
-\end{itemize}
-\end{frame}
-
-\begin{frame}
-\frametitle{over-committing}
-\begin{itemize}
-\item Comparable to those low-cost airlines ;)
-\pause
-\item ...selling more tickets than available seats
-\pause
-\item ...hoping not everyone will come ;)
-\end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
-\frametitle{over-commit settings}
-\begin{verbatim}
-/proc/sys/vm/overcommit_memory
-\end{verbatim}
-Possible settings are:
-\begin{itemize}
-\item 0: Heuristic overcommit handling (default)
-\item 1: Always overcommit
-\item 2: Don't overcommit
-\end{itemize}
-\end{frame}
-
-\begin{frame}
-\frametitle{The OOM Killer}
-...is invoked if you ask for more memory than available.\\
-\pause
-\textbf{Result}: The kernel kills a task
-\end{frame}
-
-\begin{frame}
-\frametitle{Copy-On-Write}
-\begin{itemize}
-\item completely transparently for userspace
-\item you don't need the same data twice
-\item only updated if one virtual memory area is updated
-\end{itemize}
-\end{frame}
-
-\begin{frame}
-\frametitle{Page relocation}
-\begin{itemize}
-\item AKA paging or swapping
-\item Linux can move a page to / from swap
-\item also completely transparently for userspace
-\end{itemize}
-\end{frame}
-
-\subsection{The stack}
-\begin{frame}
-\frametitle{The stack}
-\begin{itemize}
-\item Grows top - down
-\item Configurable stack size
-\item Stack grows on demand. Access beyond current size ends up in a
-''Stackfault'' which is handled by the kernel
-\item ulimit -a shows the current maximum stack size
-\item ulimit -s \emph{size} sets the maximum stack size
-\item Default maximum stack size is 8MiB
-\end{itemize}
-\end{frame}
-
-\subsection{The heap}
-
-\begin{frame}
-\frametitle{The heap: Userland handling}
-\begin{itemize}
-\item Memory is allocated using malloc()
-\item Memory is freed using free()
-\item malloc() uses the mmap() and the sbrk() system calls
-\end{itemize}
-\end{frame}
-
-\begin{frame}
-\frametitle{The heap: Userland handling}
-\begin{itemize}
-\item For small junks, malloc() allocates memory from the heap and adjusts the
-size using sbrk()
-\item For larger blocks (larger than defined in MMAP\_THRESHOLD) the memory is
-allocated as private, anonymous mapping
-\item MMAP\_THRESHOLD is 128kb by default
-\end{itemize}
-\end{frame}
-
-\begin{frame}
-\frametitle{malloc()}
-\begin{itemize}
-\item Keep over-commit in mind!
-\item If over-commit is enabled: A non-null return value from malloc() doesn't
-guarantee that the memory really is available.
-\end{itemize}
-\end{frame}
-
-\section{Do's and Dont's}
-\subsection{The heap}
-% fragmentation
-% check return value
-% ulimit (limit memory consumption)
-\begin{frame}
-\frametitle{Return value}
-Always check malloc's return value!!
-\end{frame}
-
-\begin{frame}
-\frametitle{How to avoid heap fragmentation}
-\begin{itemize}
-\item GLIBCs malloc() itself tries to avoid fragmentation
-\item The allocator can't avoid fragmentation caused by a bad application
-design!
-\item Try to re-use memory pools
-\item free memory you don't need anymore!
-\end{itemize}
-\end{frame}
-
-\begin{frame}
-\frametitle{How to limit memory consumption}
-ulimit:
-\begin{itemize}
-\item ulimit -d sets a limit for the data segment
-\item ulimit -v sets a limit for the virtual memory
-\item Check limits with ulimit -a
-\end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
-\frametitle{ulimit example}
-\scriptsize
-\begin{verbatim}
-$ ulimit -a
-core file size          (blocks, -c) 0
-data seg size           (kbytes, -d) unlimited
-scheduling priority             (-e) 20
-file size               (blocks, -f) unlimited
-pending signals                 (-i) 16382
-max locked memory       (kbytes, -l) 64
-max memory size         (kbytes, -m) unlimited
-open files                      (-n) 1024
-pipe size            (512 bytes, -p) 8
-POSIX message queues     (bytes, -q) 819200
-real-time priority              (-r) 0
-stack size              (kbytes, -s) 8192
-cpu time               (seconds, -t) unlimited
-max user processes              (-u) unlimited
-virtual memory          (kbytes, -v) unlimited
-file locks                      (-x) unlimited
-\end{verbatim}
-\end{frame}
-
-\section{Realtime}
-\subsection{General}
-\begin{frame}[fragile]
-\frametitle{Locking the memory}
-\begin{verbatim}
-/* Lock memory */
-if(mlockall(MCL_CURRENT|MCL_FUTURE) == -1) {
-        perror("mlockall failed");
-        exit(-2);
-}
-\end{verbatim}
-\end{frame}
-\subsection{Stack}
-\begin{frame}[fragile]
-\frametitle{Stack prefaulting}
-\begin{verbatim}
-#define MAX_SAFE_STACK (8*1024)
-
-void stack_prefault(void) {
-        unsigned char dummy[MAX_SAFE_STACK];
-
-        memset(&dummy, 0, MAX_SAFE_STACK);
-        return;
-}
-\end{verbatim}
-\end{frame}
-
-\subsection{Heap}
-\begin{frame}
-\frametitle{Allocations from Realtime context}
-\begin{itemize}
-\item If possible, avoid memory allocations from Realtime context
-\item Try to use a pre-allocated buffer
-\end{itemize}
-\end{frame}
-
-
-\begin{frame}[fragile]
-\frametitle{Disable malloc trimming and mmap usage}
-\begin{verbatim}
-mallopt(M_TRIM_THRESHOLD, -1);
-mallopt(M_MMAP_MAX, 0);
-\end{verbatim}
-\end{frame}
-
-\begin{frame}[fragile]
-\frametitle{Reserve process memory}
-\begin{verbatim}
-static void reserve_process_memory(int size)
-{
-   int i;
-   char *buffer;
-   
-   buffer = malloc(size);
-   
-   /* Touch each page in this piece of
-    * memory to get it mapped into RAM */
-   for (i = 0; i < size; i += sysconf(_SC_PAGESIZE))
-      buffer[i] = 0;
-   
-   free(buffer);
-}
-\end{verbatim}
-\end{frame}
-
-\section*{sources}
-\begin{frame}
-\frametitle{sources}
-\begin{thebibliography}{1}
-\bibitem{mmm} http://cftw.wordpress.com/2009/11/02/introduction-to-the-linux-memory-management/
-\bibitem{mmm} http://rt.wiki.kernel.org/
-\end{thebibliography} 
-\end{frame}
-
-\end{document}
-- 
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