Re: rt20 scheduling latency testcase and failure data

Darren Hart
2006-05-13T23:01:42Z

On Saturday 13 May 2006 11:21, Lee Revell wrote:
> On Sat, 2006-05-13 at 11:06 -0700, Darren Hart wrote:
> > 1 [softirq-timer/0]
>
> What happens if you set the softirq-timer threads to 99?
>

After setting all 4 softirq-timer threads to prio 99 I seemed to get only 2
failures in 100 runs. #51 slept too long (10ms too long!), the latency
appeared after the sleep in #90 (nearly 483ms worth). Those latencies seem
huge to me.

ITERATIONS 0-50 Passed

ITERATION 51
-------------------------------
Scheduling Latency
-------------------------------

Running 10000 iterations with a period of 5 ms
Expected running time: 50 s

ITERATION DELAY(US) MAX_DELAY(US) FAILURES
--------- --------- ------------- --------
7000 10197 10197 1

PERIOD MISSED!
scheduled delta: 4079 us
actual delta: 14263 us
latency: 10183 us
---------------------------------------
previous start: 35010197 us
now: 35011117 us
scheduled start: 35005000 us
next scheduled start is in the past!

Start Latency: 114 us: FAIL
Min Latency: 9 us: PASS
Avg Latency: 7 us: PASS
Max Latency: 10197 us: FAIL
Failed Iterations: 1

ITERATIONS 52-89 Passed

ITERATION 90
-------------------------------
Scheduling Latency
-------------------------------

Running 10000 iterations with a period of 5 ms
Expected running time: 50 s

ITERATION DELAY(US) MAX_DELAY(US) FAILURES
--------- --------- ------------- --------
2747 9 20 0

PERIOD MISSED!
scheduled delta: 4072 us
actual delta: 4079 us
latency: 6 us
---------------------------------------
previous start: 13735009 us
now: 14218183 us
scheduled start: 13740000 us
next scheduled start is in the past!

Start Latency: 112 us: FAIL
Min Latency: 8 us: PASS
Avg Latency: 2 us: PASS
Max Latency: 20 us: PASS
Failed Iterations: 0

ITERATIONS 91-99 Passed

Thanks,

--
Darren Hart
IBM Linux Technology Center
Realtime Linux Team