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Real Time in Embedded Linux System

1,334 bytes added, 10:17, 1 July 2015
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Based on free training materials from Free Electrons covering real-time (http://free-electrons.com/docs/realtime/)
Learn how to handle real-time processes and practice with the different real-time modes. Measure The purpose of this article is measure scheduling latencyin different conditions. == Setup ==
== Using high-resolution timers ==
Have a look at the [http://downloads.isee.biz/pub/files/examples/rttest.c rttest.c ] source file
Now compile this program:
Execute the program on the board
=== Testing the non-voluntary preemption kernel ===
=== Testing the voluntary preemption kernel ===Test done with linux-2.6.35.y branch from git://git.igep.es/pub/scm/linux-omap-2.6.git
Recompile your kernel with CONFIG_PREEMPT_VOLUNTARY enabled and test the program with nothing special
=== Testing the preemptible kernel ===
 
Test done with linux-2.6.35.y branch from git://git.igep.es/pub/scm/linux-omap-2.6.git
Recompile your kernel with CONFIG_PREEMPT enabled and test the program with nothing special
=== Testing the Xenomai scheduling latency ===
$ wget Test done with linux-2.6.35.y-rt branch from http://downloadgit.gnaisee.orgbiz/?p=pub/scm/xenomailinux-omap-2.6.git;a=shortlog;h=refs/stableheads/xenomailinux-2.6.035.y-rt Recompile your kernel with CONFIG_XENOMAI enabled and test the program with nothing special  # ./rttest Clock resolution (ns): 1 Measurement, please wait 1 minute... Samples: 327833 Min latency: 73 us Max latency: 9702 us Average latency: 80 us Test your program and at the same time, add some workloadto the board, by running   # stress --cpu 1 --io 2 --vm 2 --vm-bytes 128M --timeout 120s & # ./rttest Clock resolution (ns): 1 Measurement, please wait 1 minute..tar.bz2 Samples: 320301 Min latency: 63 us Max latency: 10006 us Average latency: 85 us
=== rt-tests ===Test your program again with the workload, but by running the program in the SCHED_FIFO scheduling class at priority 99
$ git clone git# stress --cpu 1 --io 2 --vm 2 --vm-bytes 128M --timeout 120s & # chrt -f -r 99 ./rttest Clock resolution (ns)://github1 Measurement, please wait 1 minute..com/clrkwllms/rt-tests.git Samples: 453705 Min latency: 18 us Max latency: 395 us Average latency: 30 us
== Links ==
** https://www.osadl.org/Latency-generator.latency-generator.0.html
** https://www.osadl.org/Visualize-the-temporal-relationship-of-L.taks-visualizer.0.html
** http://elinux.org/Realtime_Testing_Best_Practices
* Other resources
** http://www.osadl.org/Realtime-Linux.projects-realtime-linux.0.html
** https://rt.wiki.kernel.org/index.php/Main_Page
** https://www.osadl.org/fileadmin/dam/rtlws/12/Brown.pdf
** http://embedded.communities.intel.com/servlet/JiveServlet/download/4435-1248/xeno_intel.pdf
 
 
[[Category:Software distributions]][[Category:How to forge]][[Category:Software applications]]
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