* Naveen N. Rao <[email protected]> wrote:
> On 2015/06/02 09:58AM, Ingo Molnar wrote:
> >
> > * Naveen N. Rao <[email protected]> wrote:
> >
> > > On 2015/05/29 11:54AM, Ingo Molnar wrote:
> > > >
> > > > > On a related note, even though sum_exec_runtime is available
> > > > > unconditionally, I dump all zeroes in my patch if
> > > > > !sched_info_on() to make it clear that some of the fields are
> > > > > not available. Is this ok or should be display sum_exec_runtime
> > > > > regardless of sched_info?
> > > >
> > > > So I'd suggest printing -1 for non-available fields, that should be
> > > > unambigous
> > > > enough and makes it also possible to write out 0 in some cases.
> > >
> > > Per Documentation/scheduler/sched-stats.txt (and the linked latency.c
> > > there),
> > > user-space seems to be expecting unsigned values here. Would displaying
> > > -1 here
> > > be ok?
> >
> > Probably not (the code is silly, why doesn't it split up the string and use
> > atol()?) - hopefully real user-space is better? Can you try some real,
> > packaged up
> > tools that read schedstats, to see whether they work with -1?
>
> Hi Ingo,
> Sorry for the delay - I had been off on vacation.
>
> I see that quite a few packages are using /proc/<pid>/schedstat - pcp,
> systemd,
> dstat, android, among others. While most of these seem to be splitting up the
> fields properly, they are using a variant of strtoull(), which returns
> ULLONG_MAX for -1, and none of these check for that condition. If any of the
> tools use the value read to report total execution time or run delay, it will
> be
> incorrect.
>
> At this point, I feel it is better to display all the three fields in
> schedstat
> only if sched_info_on() is true, as explained above. What do you suggest?
Ok, agreed - thanks for the analysis.
Mind (re-)submitting the patches accordingly?
Thanks,
Ingo
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