2013 ufsc rt_grad_class
TRANSCRIPT
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RT OS and
RT LinuxDaniel Bristot de Oliveira
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Who I'm and what we will
talk about?
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an Operating System overview
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Operating System
Application
Hardware
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Tasks of an OS
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Hardware...
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Embedded system without OS
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OS as a library
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OS as a library
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OS as a library
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Memory Protection - MMU
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OS with a Micro-Kernel
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OS as we know
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What does Real-Time means?
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Event -> Response, latency,
response time,
deadline...
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Real-Time means
fast?
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Real Time != FAST!
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RT means
Determinism, WCET,
Response Time.
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What is a Real-Time
Operating System?
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Deterministic hardware+
Deterministic hardware abstraction+
Services with WCET+
Deterministic Resource Management=?
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Real-Time Operating System Examples
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?
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FreeRTOS
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Neutrino (QNX)
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Linux ?
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Why is Linux not a RTOS?
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Linux is too much flexible
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General Purpose OS
● Linux not is a RTOS by conception● Higher throughput rather than higher
determinism.● High latency.
● But has:● Static priority sched: FIFO and RR
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Linux as a RTOS?
● Why?● Hardware support
● ARM, MIPS, POWERPC, intel, TILE 64, ADBF...● Services
● FS, Network Stack...● Money
● Rich company X needs a low latency Oracle database.
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How Red Hat shows your Real-Time Linux
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Real-Time Linux: Past, Present, Possible
Futures...
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RTAI and Xenomai
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RT Task on Xenomai +
Non-RT on Linux... =
):) <- this is a bipolar emoticon
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PREEMPT-RT
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- latency+ control over OS tasks
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Sources of latency
● IRQ Handling● Softirq
● Preempt off● spinlocks
● IRQ off
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Preemptive lock
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Priority inversion problems...
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IRQ Handling
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How good is PREEMPT_RT Today?
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PREMPT-RT is WONDERFULL! Let's use everywhere!!!
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):)
This is another bipolar emoticon, but more happy than another...
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How expensive is PREEMP-RT?
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PREEMPT-RT
Vanilla
Concurrent channels
CP
U L
oa
d (
%)
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LITMUSRT
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A testbed for multiprocessor scheduling
in Real-Time Systems
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(Partitioned|Global|Clustered) EDF
Partitioned Fixed-Priority
PD2 (PFAIR)
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Mutual Exclusion
Interrupt Handling
Real-Time GPU Management
Tracing Tools
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How good is Litmus RT?
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Litmus RT=
a way to pick next taskwith a RT API.
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A little bit of my MS Degree dissertation...
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Questions?