[bootlin/training-materials updates] master: Revert "Real-time lab: use chrt before adding load" (425e674c)

Michael Opdenacker michael.opdenacker at bootlin.com
Fri May 21 10:03:31 CEST 2021

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/425e674c1c463c9d88b0e4bf30fe0e2f244e7e10


commit 425e674c1c463c9d88b0e4bf30fe0e2f244e7e10
Author: Michael Opdenacker <michael.opdenacker at bootlin.com>
Date:   Fri May 21 10:03:31 2021 +0200

    Revert "Real-time lab: use chrt before adding load"
    - Adding load without chrt is a way to show that
      you cannot expect correct worst case latencies
      without running your app with a real time priority
    This reverts commit ab0448b6cf93b3ac99288277f6577247233ca329.


 labs/sysdev-real-time/sysdev-real-time.tex | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/labs/sysdev-real-time/sysdev-real-time.tex b/labs/sysdev-real-time/sysdev-real-time.tex
index 2ece8cc3..d0f4ed1d 100644
--- a/labs/sysdev-real-time/sysdev-real-time.tex
+++ b/labs/sysdev-real-time/sysdev-real-time.tex
@@ -159,17 +159,15 @@ Now, do the following tests:
 \item Run the \code{rttest} program with nothing special and write
   down the results.
-\item Run \code{rttest} once again, but this time
-  using the \code{SCHED_FIFO} scheduling class at priority
-  \code{99}, using the \code{chrt} command. Without this, the kernel
-  doesn't know that your program should be given absolute priority
-  over other processes.
-\item Run \code{rttest} again through \code{chrt}, but right before,
-  add some extra load, by running \code{/root/doload 300 > /dev/null 2>&1 &}
+\item Run \code{rttest} again and at the same time, add some workload
+  to the board, by running \code{/root/doload 300 > /dev/null 2>&1 &}
   on the board, and using \code{netcat 5566} on your
   workstation in order to flood the network interface of the Xplained
   board (where \code{} is the IP address of the Xplained
+\item Run \code{rttest} once again with the workload, but by running
+  the program in the \code{SCHED_FIFO} scheduling class at priority
+  \code{99}, using the \code{chrt} command.
 \subsection{Testing the preemptible kernel}

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