[LTP] [PATCH v2] sched: starvation: Autocallibrate the timeout

[Cyril Hrubis]

Hi!
> > What kernel version do you use?
> We are now using kernel 5.15
> 
> > Do you run LTP with background tasks to keep the CPU bussy?
> Yes, we are testing LTP with Android VTS. And the test environment is under Android Launcher.
> 
> > Do you have any custom patches for kernel scheduller applied?
> I think there is no any patch applied for kernel scheduller.
> 
> > It really looks like something unexpected is happening at your end.
> 
> Actually, the same kernel version using 64bit kernel can pass the ltp test.
> 
> 
> 
> 1. for 32bit kernel, we have this log
> 
> 32bit kernel
> external/ltp/testcases/kernel/sched/cfs-scheduler/starvation.c:161: TINFO: do_test by pid 4523
> external/ltp/testcases/kernel/sched/cfs-scheduler/starvation.c:166: TINFO: main pid is 4523
> external/ltp/testcases/kernel/sched/cfs-scheduler/starvation.c:167: TINFO: child pid is 4524
> external/ltp/testcases/kernel/sched/cfs-scheduler/starvation.c:166: TINFO: main pid is 4524
> external/ltp/testcases/kernel/sched/cfs-scheduler/starvation.c:167: TINFO: child pid is 0
> external/ltp/testcases/kernel/sched/cfs-scheduler/starvation.c:176: TINFO: go loop, current pid is 4523
> external/ltp/testcases/kernel/sched/cfs-scheduler/starvation.c:145: TINFO: current ppid is 4523, current pid is 4524, go to child() start
> 
> main pid is 4523, child pid is 4524, and we only see child pid is working (checking by top)
> 
> 4524 root         20   0  14M 472K    0 R 85.7   0.0   0:14.93 starvation_v4 -t 1000000 -l 1000000 <-- cpu_load by top

So this looks like we managed to reproduce the issue the test was trying
to catch. The child is hogging the CPU and the parent process cannot
proceed. And I suppose that this happens only on 32bit because 32bit is
less tested these days.

-- 
Cyril Hrubis
chrubis@suse.cz