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

[Petr Vorel]

Hi Cyril,
all,

> 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.

I guess we can merge this, right?
Or we still not sure whether this is really kernel bug not related to the
change?

Kind regards,
Petr