Please correct me, if I am wrong, but here is my guess:
I think that the new code gives actually better numbers for kontact. Kontact
is using the cpu for very short periods, right? The old code updates utime
and stime via sampling at each timer tick. If kontact is scheduled based on
the timer tick(lets say timeout and a low amount of other interrupts) it will
start shortly after a tick. If kontact now manages to return the cpu before
the next tick, the old code would not account anything for kontact.
The new code instead, should be correct in terms of overall runtime as it
accounts the scheduled time in ns.
Why does it still shows numbers going backwards? I guess the sampled values
for stime and utime change in flight between task_utime and task_stime are
called. Lets say utime will be increased. Given the same sum_exec_runtime
that means that the result of task_stime() will get smaller at this point.
So Chucks patch only deals with sum_exec_runtime changing.
Ingo, do you have any opinion about how to proceed?
Christian
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