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Jitter Analysis

Test application: Jitter.java

The test application runs a perdioc thread at different periods starting at 500ms and going down until the jitter is higher than 50% or a deadline miss occurs. The period thread itself performs some small memory allocation and time calculation to measure the actual period in each iteration. A background task at low priority performs an allocation intensive computation.

For each period length, the following data is collectoed:

the minumum and maximum actual execution time for one period
the average execution time for one period
the standard deviation of the actual period measured from the period desired (the Jitter)
The number of iterations used in the measurement

Jitter Analysis on VxWorks/PPC

Test system: MEN A12-6U VMEbus PowerPC, MPC8245 (PPC603), 300MHz, VxWorks 5.4

The system timer was set to an accuracy of 0.5ms. With this setting, a minimal Jitter is achieved for periods down to 1ms

Test results:

Jitter test: JamaicaVM 2.3beta time resolution  500.00us will take about    1.50s  per iteration.
Period  500.00ms: min= 499.50ms (100%) max= 500.00ms (100%) average= 499.83ms sigma= 288.67us (  0%) (3 iterations)
Period  400.00ms: min= 399.50ms (100%) max= 400.00ms (100%) average= 399.83ms sigma= 288.67us (  0%) (3 iterations)
Period  300.00ms: min= 299.50ms (100%) max= 300.00ms (100%) average= 299.90ms sigma= 223.60us (  0%) (5 iterations)
Period  200.00ms: min= 199.50ms (100%) max= 200.00ms (100%) average= 199.92ms sigma= 188.98us (  0%) (7 iterations)
Period  150.00ms: min= 149.50ms (100%) max= 150.00ms (100%) average= 149.95ms sigma= 158.11us (  0%) (10 iterations)
Period  100.00ms: min=  99.50ms (100%) max= 100.00ms (100%) average=  99.96ms sigma= 129.09us (  0%) (15 iterations)
Period   75.00ms: min=  74.50ms ( 99%) max=  75.00ms (100%) average=  74.97ms sigma= 111.80us (  0%) (20 iterations)
Period   50.00ms: min=  49.50ms ( 99%) max=  50.00ms (100%) average=  49.98ms sigma=  91.28us (  0%) (30 iterations)
Period   40.00ms: min=  40.00ms (100%) max=  40.00ms (100%) average=  40.00ms sigma=   0.00ns (  0%) (37 iterations)
Period   30.00ms: min=  29.50ms ( 98%) max=  30.50ms (102%) average=  30.00ms sigma= 100.00us (  0%) (50 iterations)
Period   20.00ms: min=  20.00ms (100%) max=  20.00ms (100%) average=  20.00ms sigma=   0.00ns (  0%) (75 iterations)
Period   15.00ms: min=  14.50ms ( 97%) max=  15.00ms (100%) average=  14.99ms sigma=  50.00us (  0%) (100 iterations)
Period   10.00ms: min=   9.50ms ( 95%) max=  10.00ms (100%) average=   9.99ms sigma=  40.82us (  0%) (150 iterations)
Period    7.50ms: min=   7.00ms ( 93%) max=   7.50ms (100%) average=   7.49ms sigma=  35.35us (  0%) (200 iterations)
Period    5.00ms: min=   4.50ms ( 90%) max=   5.00ms (100%) average=   4.99ms sigma=  28.86us (  1%) (300 iterations)
Period    4.00ms: min=   3.50ms ( 88%) max=   4.00ms (100%) average=   3.99ms sigma=  25.81us (  1%) (375 iterations)
Period    3.00ms: min=   2.50ms ( 83%) max=   3.00ms (100%) average=   2.99ms sigma=  22.36us (  1%) (500 iterations)
Period    2.00ms: min=   1.50ms ( 75%) max=   2.00ms (100%) average=   1.99ms sigma=  18.25us (  1%) (750 iterations)
Period    1.50ms: min=   1.50ms (100%) max=   1.50ms (100%) average=   1.50ms sigma=   0.00ns (  0%) (1000 iterations)
Period    1.00ms: min= 500.00us ( 50%) max=   1.00ms (100%) average= 999.66us sigma=  12.90us (  1%) (1500 iterations)
Period  750.00us: min=   0.00ns (  0%) max=   1.00ms (133%) average= 749.75us sigma= 250.49us ( 33%) (2000 iterations)
Overrun for period  500.00us after 1 iterations!
Jitter analysis complete. Average jitter below 50% for periods  750.00us and higher.

Jitter Analysis on QNX 6.2.1/x86

Test system: AMD XP 2000+ on 1,53 GHz, 512 MB RAM

Builder command: jamaica -numThreads 10 Jitter

Test results:

Jitter test: JamaicaVM 2.3beta time resolution 20.00ms will take about 1.50s  per iteration.
Period  500.00ms: min= 499.92ms (100%) max= 499.92ms (100%) average= 499.92ms sigma=  76.66us (  0%) (3 iterations)
Period  400.00ms: min= 399.93ms (100%) max= 399.93ms (100%) average= 399.93ms sigma=  61.00us (  0%) (3 iterations)
Period  300.00ms: min= 299.95ms (100%) max= 299.95ms (100%) average= 299.95ms sigma=  45.80us (  0%) (5 iterations)
Period  200.00ms: min= 199.96ms (100%) max= 199.97ms (100%) average= 199.96ms sigma=  30.57us (  0%) (7 iterations)
Period  150.00ms: min= 149.97ms (100%) max= 149.97ms (100%) average= 149.97ms sigma=  23.00us (  0%) (10 iterations)
Period  100.00ms: min=  99.98ms (100%) max=  99.98ms (100%) average=  99.98ms sigma=  15.34us (  0%) (15 iterations)
Period   75.00ms: min=  74.98ms (100%) max=  74.98ms (100%) average=  74.98ms sigma=  11.46us (  0%) (20 iterations)
Period   50.00ms: min=  49.99ms (100%) max=  49.99ms (100%) average=  49.99ms sigma=   7.64us (  0%) (30 iterations)
Period   40.00ms: min=  39.99ms (100%) max=  39.99ms (100%) average=  39.99ms sigma=   6.11us (  0%) (37 iterations)
Period   30.00ms: min=  29.99ms (100%) max=  29.99ms (100%) average=  29.99ms sigma=   4.60us (  0%) (50 iterations)
Period   20.00ms: min=  19.99ms (100%) max=  19.99ms (100%) average=  19.99ms sigma=   3.06us (  0%) (75 iterations)
Period   15.00ms: min=  14.99ms (100%) max=  14.99ms (100%) average=  14.99ms sigma=   2.33us (  0%) (100 iterations)
Period   10.00ms: min=   8.99ms ( 90%) max=   9.99ms (100%) average=   9.99ms sigma=  81.82us (  1%) (150 iterations)
Period    7.50ms: min=   6.99ms ( 93%) max=   7.99ms (100%) average=   7.49ms sigma= 499.92us (  7%) (200 iterations)
Period    5.00ms: min=   4.99ms (100%) max=   5.00ms (100%) average=   4.99ms sigma= 873.00ns (  0%) (300 iterations)
Period    4.00ms: min=   3.99ms (100%) max=   4.00ms (100%) average=   3.99ms sigma= 783.00ns (  0%) (375 iterations)
Period    3.00ms: min=   2.99ms (100%) max=   3.00ms (100%) average=   2.99ms sigma= 676.00ns (  0%) (500 iterations)
Period    2.00ms: min=   1.99ms (100%) max=   2.00ms (100%) average=   1.99ms sigma= 552.00ns (  0%) (750 iterations)
Period    1.50ms: min= 999.00us ( 67%) max=   2.00ms (133%) average=   1.49ms sigma= 499.92us ( 33%) (1000 iterations)
Period    1.00ms: min= 999.00us (100%) max=   1.00ms (100%) average= 999.84us sigma= 390.00ns (  0%) (1500 iterations)
Overrun for period  750.00us after 2 iterations!

Jitter Analysis on rhawk-Linux/x86

Test system: Intel Xeon 2.80GHz, 2 GB RAM

Builder command: jamaica -numThreads 10 Jitter -destination Jitter -constGCwork=10 -priMap=1..10=1..10,11..39=11..39

Test results:

Jitter test: JamaicaVM 2.7beta time resolution   20.00ms will take about    1.50s  per iteration.
Period  500.00ms: min= 499.99ms (100%) max= 500.00ms (100%) average= 499.99ms sigma=   5.29us (  0%) (3 iterations)
Period  400.00ms: min= 399.98ms (100%) max= 400.00ms (100%) average= 399.99ms sigma=  10.63us (  0%) (3 iterations)
Period  300.00ms: min= 299.99ms (100%) max= 300.01ms (100%) average= 299.99ms sigma=   7.08us (  0%) (5 iterations)
Period  200.00ms: min= 199.99ms (100%) max= 200.00ms (100%) average= 200.00ms sigma=   4.35us (  0%) (7 iterations)
Period  150.00ms: min= 149.99ms (100%) max= 150.00ms (100%) average= 150.00ms sigma=   3.57us (  0%) (10 iterations)
Period  100.00ms: min=  99.98ms (100%) max= 100.01ms (100%) average=  99.99ms sigma=   6.76us (  0%) (15 iterations)
Period   75.00ms: min=  74.98ms (100%) max=  75.01ms (100%) average=  75.00ms sigma=   6.88us (  0%) (20 iterations)
Period   50.00ms: min=  49.97ms (100%) max=  50.01ms (100%) average=  49.99ms sigma=   8.13us (  0%) (30 iterations)
Period   40.00ms: min=  39.98ms (100%) max=  40.01ms (100%) average=  39.99ms sigma=  10.02us (  0%) (37 iterations)
Period   30.00ms: min=  29.96ms (100%) max=  30.03ms (100%) average=  29.99ms sigma=  14.64us (  0%) (50 iterations)
Period   20.00ms: min=  19.98ms (100%) max=  20.01ms (100%) average=  20.00ms sigma=   6.09us (  0%) (75 iterations)
Period   15.00ms: min=  14.96ms (100%) max=  15.03ms (100%) average=  15.00ms sigma=  11.34us (  0%) (100 iterations)
Period   10.00ms: min=   9.96ms (100%) max=  10.03ms (100%) average=   9.99ms sigma=   9.83us (  0%) (150 iterations)
Period    7.50ms: min=   7.47ms (100%) max=   7.52ms (100%) average=   7.49ms sigma=   8.70us (  0%) (200 iterations)
Period    5.00ms: min=   4.97ms ( 99%) max=   5.02ms (101%) average=   5.00ms sigma=   8.60us (  0%) (300 iterations)
Period    4.00ms: min=   3.96ms ( 99%) max=   4.03ms (101%) average=   4.00ms sigma=   7.13us (  0%) (375 iterations)
Period    3.00ms: min=   2.96ms ( 99%) max=   3.03ms (101%) average=   2.99ms sigma=  10.79us (  0%) (500 iterations)
Period    2.00ms: min=   1.93ms ( 97%) max=   2.05ms (103%) average=   1.99ms sigma=  13.72us (  1%) (750 iterations)
Period    1.50ms: min=   1.44ms ( 96%) max=   1.54ms (103%) average=   1.49ms sigma=  12.39us (  1%) (1000 iterations)
Period    1.00ms: min= 932.00us ( 93%) max=   1.05ms (105%) average= 999.98us sigma=   9.09us (  1%) (1500 iterations)
Period  750.00us: min= 682.00us ( 91%) max= 801.00us (107%) average= 749.98us sigma=   6.93us (  1%) (2000 iterations)
Period  500.00us: min= 455.00us ( 91%) max= 542.00us (108%) average= 499.99us sigma=   4.47us (  1%) (3000 iterations)
Period  400.00us: min= 364.00us ( 91%) max= 439.00us (110%) average= 399.99us sigma=   3.05us (  1%) (3750 iterations)
Period  300.00us: min= 284.00us ( 95%) max= 318.00us (106%) average= 299.99us sigma=   2.03us (  1%) (5000 iterations)
Period  200.00us: min= 189.00us ( 95%) max= 210.00us (105%) average= 199.99us sigma=   1.76us (  1%) (7500 iterations)
Period  150.00us: min= 124.00us ( 83%) max= 178.00us (119%) average= 149.99us sigma=   1.70us (  1%) (10000 iterations)
Overrun for period  100.00us after 8 iterations!