[bootlin/training-materials updates] master: preempt-rt: More changes to the slides (a504bbdb)

[Maxime Chevallier]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/a504bbdbc84e6a50ff0bc2d5c89a55dd2455f5f5

>---------------------------------------------------------------

commit a504bbdbc84e6a50ff0bc2d5c89a55dd2455f5f5
Author: Maxime Chevallier <maxime.chevallier at bootlin.com>
Date:   Wed Jan 18 18:51:12 2023 +0100

    preempt-rt: More changes to the slides
    
    Signed-off-by: Maxime Chevallier <maxime.chevallier at bootlin.com>


>---------------------------------------------------------------

a504bbdbc84e6a50ff0bc2d5c89a55dd2455f5f5
 .../realtime-linux-application-development.tex     |  3 ++-
 .../realtime-linux-configuration.tex               | 27 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/slides/realtime-linux-application-development/realtime-linux-application-development.tex b/slides/realtime-linux-application-development/realtime-linux-application-development.tex
index 18a05573..7670adee 100644
--- a/slides/realtime-linux-application-development/realtime-linux-application-development.tex
+++ b/slides/realtime-linux-application-development/realtime-linux-application-development.tex
@@ -192,11 +192,12 @@ pthread_attr_setschedparam(&attr, &parm);
 \begin{frame}
 	\frametitle{Memory management}
 	\begin{itemize}
-		\item Call \code{mlockall()} at init to lock all memory regions
+		\item Call \code{mlockall(MCL_CURRENT | MCL_FUTURE)} at init to lock all memory regions
 		\item Allocate all memory and access it at initialization
 		\item Don't call \code{fork()}, since the child will copy-on-write pages
 		\item Avoid using mmap'd memory, since ranges aren't reused after free
 		\item malloc's behaviour can be tuned not to use mmap : \code{mallopt(M_MMAP_MAX, 0)}
+		\item We also must configure malloc not to trim the allocated space : \code{mallopt(M_TRIM_THRESHOLD, -1)}
 	\end{itemize}
 \end{frame}
 
diff --git a/slides/realtime-linux-configuration/realtime-linux-configuration.tex b/slides/realtime-linux-configuration/realtime-linux-configuration.tex
index 58b578e6..ff5f683b 100644
--- a/slides/realtime-linux-configuration/realtime-linux-configuration.tex
+++ b/slides/realtime-linux-configuration/realtime-linux-configuration.tex
@@ -48,6 +48,32 @@
 	\code{isolcpus=0,2,3}
 \end{frame}
 
+\begin{frame}
+	\frametitle{CPU Isolation - cpusets}
+	\begin{itemize}
+		\item \code{cpuset} is a mechanism allowing to subdivide the CPU scheduling pool
+		\item They are created at runtime, through the \code{cpusetfs}
+			\begin{itemize}
+				\item \code{mount -t cpuset none /dev/cpuset}
+			\end{itemize}
+		\item cpusets are created at will in the cpuset main directory
+			\begin{itemize}
+				\item \code{mkdir /dev/cpuset/rt-set}
+				\item \code{mkdir /dev/cpuset/non-rt-set}
+			\end{itemize}
+		\item Each cpuset is assigned a pool of cpu cores
+			\begin{itemize}
+				\item \code{/bin/echo 2,3 > /dev/cpuset/rt-set}
+				\item \code{/bin/echo 0,1 > /dev/cpuset/non-rt-set}
+			\end{itemize}
+		\item We can then select which task gets to run in each cpuset
+			\begin{itemize}
+				\item \code{while read i; do /bin/echo $i; done < /dev/cpuset/tasks > /dev/cpuset/nontrt-set/tasks}
+				\item \code{/bin/echo $$ > /dev/cpuset/rt-set/tasks}
+			\end{itemize}
+	\end{itemize}
+\end{frame}
+
 % irq assignment
 \begin{frame}
 	\frametitle{IRQ affinity}
@@ -74,6 +100,7 @@
 		\item \code{/proc/sys/kernel/sched_rt_period_us} defines a window in microseconds that the scheduler will share between RT and non-RT tasks
 		\item \code{/proc/sys/kernel/sched_rt_runtime_us} defines how-much of that window is going to be dedicated to RT tasks.
 		\item The default values allocates 95\% of the CPU time to RT tasks
+		\item This mechanism is also called \textbf{RT Throttling}
 	\end{itemize}
 \end{frame}