Messages in this thread | | | From | Darren Hart <> | Subject | Re: rt20 scheduling latency testcase and failure data | Date | Mon, 15 May 2006 14:49:20 -0700 |
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On Monday 15 May 2006 04:20, Sébastien Dugué wrote: > On Sat, 2006-05-13 at 11:06 -0700, Darren Hart wrote: > > These tests are running on a 4 way opteron at 2 GHz with 4 GB RAM. I > > have attached the .config and a listing of all the rt tasks running on > > the system (which addresses the questions regarding priority setup, IRQ > > handlers, and softirqs - all default). I am running with the futex > > priority based wakeup patches from Sebastien Duque, but I don't think > > this test excercises those paths. > > Which watchdog are you using here? Have you tried without the > watchdog?
Those are the softlockup watchdog threads (kernel/softlockup.c). They run once a second and reports a bug if the watchdog failed to run in 10 seconds. It is difficult to reproduce but at run 126 (1,260,000 iterations) it finally failed. Note that I am only counting runs that completely miss an entire period as a failure for the purposes of this test. I want to knock out the 10+ms latencies before I concern myself too much with the >100us failures :-)
-------------------- ITERATION 26 -------------------- ------------------------------- Scheduling Latency -------------------------------
Running 10000 iterations with a period of 5 ms Expected running time: 50 s
ITERATION DELAY(US) MAX_DELAY(US) FAILURES --------- --------- ------------- --------
PERIOD MISSED! scheduled delta: 4076 us actual delta: 14892 us latency: 10815 us --------------------------------------- previous start: 18365818 us now: 18366739 us scheduled start: 18360000 us next scheduled start is in the past!
Start Latency: 106 us: FAIL Min Latency: 8 us: PASS Avg Latency: 4 us: PASS Max Latency: 10818 us: FAIL Failed Iterations: 1
It's interesting, this 10ms latency seems to be the most common result. I'm going to take a look at ingo's tracing script now, more info a bit later...
-- Darren Hart IBM Linux Technology Center Realtime Linux Team
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