Re: [RFC PATCH] sched/deadline: show leftover runtime and abs deadline in /proc/-/sched

[Peter Zijlstra]

On Tue, Oct 25, 2016 at 12:32:53AM +0200, Tommaso Cucinotta wrote:
> Hi all,
> 
> this is a tiny patch providing readings of the current (leftover)
> runtime and absolute deadline in /proc/*/sched. Mostly useful for
> debugging, I heard others playing with SCHED_DEADLINE had some need
> for similar patches as well.
> 
> In addition to debugging, reading the leftover runtime is generally
> useful for adaptive/incremental RT logics that need to check whether
> there's enough runtime left for refining the computed result, or just
> use what we've computed so far and block till the next instance.
> Also, knowing what the absolute scheduling deadline is (along with
> what clock it refers to) might be useful for synchronization purposes.
> (albeit, for real production code, I wouldn't like to parse /proc anyway,
> rather I'd prefer to retrieve those params via eg sched_getscheduler()?)

So for programmatic use, this interface is not recommended. For
debugging this is fine.

Not sure what form the programmatic interface should take, we have
precedence in sys_sched_rr_get_interval() for a syscall (we could even
abuse this one).

Anybody any ideas?