Messages in this thread | | | Date | Thu, 25 Jun 2015 14:12:11 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] proc/schedstat: Expose /proc/<pid>/schedstat if delay accounting is enabled |
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* Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> wrote:
> On 2015/06/02 09:58AM, Ingo Molnar wrote: > > > > * Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> 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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