realtimeandembeddedsystems_part4 mathhoang vietnam_hoangminhnguyen

8/8/2019 RealTimeAndEmbeddedSystems_Part4 mathhoang vietnam_hoangminhnguyen

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8/20/2010 Embedded Systems Course: Measuring Execution Time and Real-Time Performance - 2010 4

What exactly is beingmeasured ?

Real-Time Scheduling AnalysisTask Execution TimePeriodic Time of Task

The effect of RTOS OverheadContext SwitchInterrupt Processing

The effect of RTOS ServicesMessage PassingSemaphore ProcessingMemory Allocation/Deallocation


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Measurement Methods

Stop-watchProgram starts, state the watch. Program ends,stop the watch and read the timeToo low in accuracy for real-time codeIgnore this manual method

Software AnalyzerWindView, Tornado Environment (VxWorks)ARM RealView ProfilerReal-Time Trace, Keil ARM Development Tools


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Measurement Methods WindView


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Measurement Methods Using Timer Services

start = OSTimerGet();do stuff;finish = OSTimerGet();total = (finish start)/CLOCK_TICKS;

Measurement

Accuracy depends on the tick resolution


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Code Execution TimeEstimation

T = I c * CPI / f


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Measurement Methods Hardware Tools

The best tools for accuratelymeasuring execution time

Hook up the probes to the CPU pinsThe embedded application is designedwith at least one such port dedicated

to testing and debuggingThe software must send the signals tothese dedicated port pins


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Measurement Methods Hardware Tools

Using LPC2294s GPIO portpins to measure theexecution time


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Measurement Methods Logic Analyzer


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Measurement Methods Oscilloscope


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Measurement Methods

Must setup macros for writing theoutput port

#define MEZ_START(id)output(dioport,0x50|id&0xF)

#define MEZ_STOP(id)output(dioport,0x60|id&0xF)


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Measuring Task Execution


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Measuring Task Execution

e task c = (55.081 28.677) (3.0669 +5.0944 + 3.3741 + 3.0464) = 11.8222msec


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Measuring Task Execution Effectof Context Switch Overhead

e 1,1 = t g ; e 2,1 = t c ; e 3,1 = t a e 2,2 = t f +t h +2 thr ; e 3,2 = t b +t d +2 thr e idle = t y +t z +4 thr ; e 3,3 = t e +t i +t k +4 thr Whenever a high priority task preempts a low-priority task, the preemptionoverhead ( thr ) is added to the execution time of the lower priority task


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Need this overhead for each task is constantSupposing the start task event was logged

before the overhead, and the end task eventwas logged after the overhead

e 1,1 = t g + 2 thr ; e 2,1 = t c + 2 thr ; e 3,1 = t a + 2 thr

e 2,2 = t f +t h +2 thr ; e 3,2 = t b +t d +2 thr e idle = t y +t z ; e 3,3 = t e +t i +t k +2 thr


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( 2. )max min . / 1,1{1 } { }

where S { . | 1, ..., ; 1, ..., / }i

The entire task set is feasible by RMS if and only if

e ji L t p j ji n t S i t

k p j i k p p j i j


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Measuring Time of TaskContext Switch

Using two periodic tasks each at a different priorityThe slowest task toggles bit on a GPIO pin connecting to channel 1The other toggles bit on another GPIO pin connecting to channel 2

2 thr = t 1 t 2 t 3


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Measuring Time of InterruptLatency

Force a software interrupt

Toggle a GPIO pin

Toggle a GPIO pin


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Measuring Time of RTOSsServices

Message PassingSemaphore ProcessingMemory Allocation/Deallocation


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Reference

David B. Stewart, Measuring Execution Time and Real-Time Performance, Embedded SystemsConference, Boston, September 2006

William Lamie and John Carbone, Measure your RTOSs Real -Time Performance,http://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performance , 2007Phillip A. Laplante, Real-Time System Design and Analysis An Engineers Handbook, John Wiley &Sons, Inc., Third Edition, 2004
http://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performancehttp://www.eetimes.com/design/automotive-design/4007081/Measure-your-RTOS-s-real-time-performance

realtimeandembeddedsystems_part4 mathhoang vietnam_hoangminhnguyen

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