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Introduction to RTOS About SwiftACT • A Technology services startup company o Under establishment • Areas of specialties: o o Mobile telecommunication services development Embedded systems development • Types of services: o o o o Consultation Managed services Sourcing Training Amr Ali Abdel-Naby@2010 Introduction to RTOS About Me • Graduated 2004 o ECE, ASU: yrs distinction • 5+ years in embedded systems development o SDLC, Apps, MW, DD, Porting, • 3+ years in SW engineering o PSP, CMMI, Systematic reuse, • 3+ years in SW testing o IBM certified, ISTQB certified, Amr Ali Abdel-Naby@2010 Introduction to RTOS Copyright • Materials in this course is the property of Amr Ali Abdel-Naby • Reproduction or transmission of the materials in any manner without the copyright owner permission is a law violation Amr Ali Abdel-Naby@2010 Introduction to RTOS Outline • • • • • • Introduction Tasks Semaphores Message Queues Other Kernel Objects Other Kernel Services Amr Ali Abdel-Naby@2010 Introduction to RTOS Outline • • • • • • Introduction Tasks Semaphores Message Queues Other Kernel Objects Other Kernel Services Amr Ali Abdel-Naby@2010 Introduction to RTOS Brief History of Operating Systems • Programs of primitive times o o Tight integration of SW + HW  Low portability Difficult and costly to maintain Modularity Abstraction GPOS Evolution of OS Interconnectivity Amr Ali Abdel-Naby@2010 RTOS Introduction to RTOS RTOS vs GPOS • RTOS == GPOS o o o Multitasking SW + HW management HW abstraction Amr Ali Abdel-Naby@2010 • RTOS != GPOS o o o o o o More reliable Scalable Faster Reduced memory needs ROM or RAM bootable Portable Introduction to RTOS GPOS or RTOS for embedded systems • GPOS can run on embedded systems with high memory and soft real-time requirements • RTOS is more suitable for low memory and hard real-time requirements • Many embedded systems run without RTOS! Amr Ali Abdel-Naby@2010 Introduction to RTOS RTOS Definition • A program that schedules execution in a timely manner, manages system resources, and provides a consistent foundation for developing application code • A kernel is the RTOS heart Application RTOS C/C++ Library • Kernel = Scheduler + Objects + Services Amr Ali Abdel-Naby@2010 File Systems Network Protocols Introduction to RTOS Kernel Other Device Components Drivers Hardware Scheduler • Which task will run next? o Scheduler has the answer • Scheduler = Scheduling algorithm + Dispatcher Amr Ali Abdel-Naby@2010 Introduction to RTOS Scheduling Algorithm • AKA scheduling policy • Most kernels support: o o Preemptive priority based algorithm Round-Robin algorithm Preemptive priority based algorithm T3 Priority T2 Priority T2 T1 Round-Robin algorithm T1 T4 T1 T2 T1 Time Time Amr Ali Abdel-Naby@2010 T3 Introduction to RTOS T2 Dispatcher • Performs context switch • Lets see an example of a context switch o Click Here Amr Ali Abdel-Naby@2010 Introduction to RTOS Objects • Building blocks for system development • Most common objects are: o o o Tasks Semaphores Message queues Amr Ali Abdel-Naby@2010 Introduction to RTOS Services • They perform operations on objects • Or provide other operations like: o o o o Timer management Interrupt handling Device I/O Memory management Amr Ali Abdel-Naby@2010 Introduction to RTOS C/Cs of RTOS • Reliability • Predictability • Performance • Compactness • Scalability Amr Ali Abdel-Naby@2010 Introduction to RTOS Reliability • How long systems can operate without human interaction? • Different reliability may be required • Reliable system = Available and does not fail • Measured by downtime per year Amr Ali Abdel-Naby@2010 Introduction to RTOS Predictability • Real-time System = Correct functionality + Correct timing • Predictable RTOS = Deterministic RTOS o o Completion of OS calls occurs within known timeframes Variance in response times is very small Amr Ali Abdel-Naby@2010 Introduction to RTOS Performance • RTS must be fast enough • CPU performance is measured in MIPS • Throughput measures overall system performance o o o SW + HW Rate of generating output by a system Measured in bps • WCET of a RTS must be known o RTOS per se does not specify performance Amr Ali Abdel-Naby@2010 Introduction to RTOS Compactness • Embedded systems have constrained memory • RTOS must be small and efficient • Designers must understand both the static and dynamic memory consumption of the RTOS and the application that will run on it Amr Ali Abdel-Naby@2010 Introduction to RTOS Scalability • RTOS is used in a variety of systems • They should scale up or down to meet different requirements • Modular deign of RTOS aids scalability Amr Ali Abdel-Naby@2010 Introduction to RTOS [...]... understand both the static and dynamic memory consumption of the RTOS and the application that will run on it Amr Ali Abdel-Naby@2010 Introduction to RTOS Scalability • RTOS is used in a variety of systems • They should scale up or down to meet different requirements • Modular deign of RTOS aids scalability Amr Ali Abdel-Naby@2010 Introduction to RTOS ... Abdel-Naby@2010 Introduction to RTOS Objects • Building blocks for system development • Most common objects are: o o o Tasks Semaphores Message queues Amr Ali Abdel-Naby@2010 Introduction to RTOS Services • They perform operations on objects • Or provide other operations like: o o o o Timer management Interrupt handling Device I/O Memory management Amr Ali Abdel-Naby@2010 Introduction to RTOS C/Cs of RTOS •... Abdel-Naby@2010 Introduction to RTOS Performance • RTS must be fast enough • CPU performance is measured in MIPS • Throughput measures overall system performance o o o SW + HW Rate of generating output by a system Measured in bps • WCET of a RTS must be known o RTOS per se does not specify performance Amr Ali Abdel-Naby@2010 Introduction to RTOS Compactness • Embedded systems have constrained memory • RTOS must... Ali Abdel-Naby@2010 Introduction to RTOS Reliability • How long systems can operate without human interaction? • Different reliability may be required • Reliable system = Available and does not fail • Measured by downtime per year Amr Ali Abdel-Naby@2010 Introduction to RTOS Predictability • Real-time System = Correct functionality + Correct timing • Predictable RTOS = Deterministic RTOS o o Completion... algorithm + Dispatcher Amr Ali Abdel-Naby@2010 Introduction to RTOS Scheduling Algorithm • AKA scheduling policy • Most kernels support: o o Preemptive priority based algorithm Round-Robin algorithm Preemptive priority based algorithm T3 Priority T2 Priority T2 T1 Round-Robin algorithm T1 T4 T1 T2 T1 Time Time Amr Ali Abdel-Naby@2010 T3 Introduction to RTOS T2 Dispatcher • Performs context switch •