Linux Plumbers 2018 report

It was a success! This year I ended up making five talks! All related to real-time Linux, as expected. As feedback, I think that the most important are: – The idea of using automata model for explaining Linux’s dynamics and, mainly, to verify the behavior of the system was very welcome by the community. They want even more: To extend the idea to other subsystems of the kernel. – The semi-partitioned scheduler is a wish for Linux! – We need new metrics for the RT, and we need to integrate this with probabilistic execution time analysis. I was already planning…

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Real-time Linux Summit 2018 – My slides

Hi! Here are the slides of my presentation in this year’s Real-time Linux Summit. The title is “Mind the gap: between real-time Linux and real-time theory (Part I).” It is about the creation of a formal model for tasks on Linux, in the intersection of the viewpoint of real-time Linux developers and real-time researchers. I received excellent feedback from the Linux community. There is interest in applying my method for the verification of the PREEMPT-RT kernel, even for areas that I was not expecting, like static code analysis. For a computer scientist, seeing practical results of applying a formal method…

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Modeling the Behavior of Threads in the PREEMPT_RT Linux Kernel Using Automata: All material

From the communication: “On behalf of the Program Committee for EWiLi 2018, I am pleased to inform you that the following submission has been accepted for publication in the workshop: Modeling the Behavior of Threads in the PREEMPT_RT Linux Kernel Using Automata” The best thing is that all the revisor’s comments are constructive. All three revisors gave an “accepted” on the paper (a paper can be: accepted, weakly accepted, borderline, weakly rejected, rejected)! You can find the paper in this link: Paper The presentation in this link: Slides The model in this link: Model The code is in this link:…

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Setting real-time priorities to services using systemd

Systemd supports the setup of real-time priority to services launched during the boot process. This is done using the following Directives in the Service section: CPUSchedulingPolicy= Sets the CPU scheduling policy for executed processes. Takes one of other, batch, idle, fifo or rr. CPUSchedulingPriority= Sets the CPU scheduling priority for executed processes. The available priority range depends on the selected CPU scheduling policy. For real-time scheduling policies, an integer between 1 (lowest priority) and 99 (highest priority) can be used. Example This is the mcelog service unity: [Unit] Description=Machine Check Exception Logging Daemon [Service] ExecStart=/usr/sbin/mcelog –ignorenodev –daemon –foreground [Install] WantedBy=multi-user.target…

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__schedule() being called twice, the second in vain

Here is one example of the trace of the problem I reported in this e-mail to the LKML Note Patch accepted! This patch is the first change that was proposed by the analysis of the task model I am developing in my Ph.D. Thesis. Trace setup The trace setup I am using is the following: # cd /sys/kernel/debug/tracing/ # echo preempt_schedule_irq schedule schedule_preempt_disabled schedule_idle schedule_user >> set_graph_function ; done # echo function_graph > current_tracer # echo sched:sched_switch sched:sched_wakeup > set_event # echo irq_vectors >> set_event # echo $(( 1408 * 100 )) > buffer_size_kb # echo > trace In addition,…

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