1. RT OS
and
RT Linux
Daniel Bristot de Oliveira

2. Who I'm and what we will
talk about?

3. an Operating
System overview

4. Application
Operating System
Hardware

5. Tasks of an OS

6. Hardware...

7. Embedded system without OS

8. OS as a library

9. OS as a library

10. OS as a library

11. Memory Protection - MMU

12. OS with a Micro-Kernel

13. OS as we know

14. What does Real-Time
means?

15. Event -> Response,
latency,
response time,
deadline...

16. Real-Time means
fast?

17. Real Time != FAST!

18. RT
means
Determinism,
WCET,
Response Time.

19. What is a Real-Time
Operating System?

20. Deterministic hardware
+
Deterministic hardware abstraction
+
Services with WCET
+
Deterministic Resource Management
=
?

21. Real-Time Operating
System Examples

22. ?

23. FreeRTOS

24. Neutrino (QNX)

25. Linux ?

26. Why
is Linux not a
RTOS?

27. Linux is too much flexible

28. 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

29. Linux as a RTOS?
●
Why?
●
Hardware support
●
●
Services
●
●
ARM, MIPS, POWERPC, intel, TILE 64, ADBF...
FS, Network Stack...
Money
●
Rich company X needs a low latency Oracle
database.

30. How
Red Hat shows your Real-Time
Linux

31. Real-Time Linux: Past,
Present, Possible
Futures...

32. RTAI and Xenomai

34. RT Task on Xenomai
+
Non-RT on Linux...
=
):)
<- this is a bipolar emoticon

35. PREEMPT-RT

36. - latency
+ control over OS tasks

37. Sources of latency
●
IRQ Handling
●
●
Preempt off
●
●
Softirq
spinlocks
IRQ off

38. Preemptive lock

39. Priority inversion
problems...

41. IRQ Handling

45. How good is PREEMPT_RT Today?

47. PREMPT-RT is
WONDERFULL!
Let's use everywhere!!!

48. )
:)
This is another bipolar emoticon, but more happy
than another...

49. How expensive is
PREEMP-RT?

50. 50
45
40
35
CPU Load (%)
30
PREEMPT-RT
Vanilla
25
20
15
10
5
0
12
24
36
Concurrent channels
60

51. LITMUS
RT

52. A testbed for multiprocessor
scheduling
in Real-Time Systems

53. (Partitioned|Global|Clustered) EDF
Partitioned Fixed-Priority
PD2 (PFAIR)

54. Mutual Exclusion
Interrupt Handling
Real-Time GPU Management
Tracing Tools

55. How good is Litmus RT?

57. Litmus RT
=
a way to pick next task
with a RT API.

58. A little bit of my MS Degree dissertation...

59. Questions?