Hi all, +cc-ing Alessio, who has been working on this just recently on Android (will tell more answering on a different msg). On 20/08/2018 18:45, Tim Blechmann wrote:
the mach API also has this notion of "period == 0", but apart from that it's quite similar.
in terms of API, XNU time constrained threads look like DEADLINE, however in terms of kernel behavior/implementation behind that, it's something completely different: last time I had a glance at this, it was .... ehm .... probably just during that old Linux Audio Conference (LAC) back in 2011, where the take away was: 1) in the kernel there's nothing like the CBS or deadline-based scheduling, but just a heuristic boosting a bit more those tasks, accompanied by usual heuristics to de-boost in case the task becomes CPU-intensive (similar to CFS heuristics for interactive-vs-batch); 2) the only user of that API seemed to be some sound daemon on OS-X, that had an almost random value set as "runtime", accompanied by a comment "this just works" ;-P
But, it was long ago, if anyone has a pointer to what XNU does with time constrained threads in these days....
apart from that, i'm only missing two features: * using SCHED_DEADLINE from user applications is kind of a showstopper for me
unprivileged tasks using DEADLINE remained a request for quite a long time -- that old single-processor implementation (AQuoSA) we used long ago with JACK had such a feature, that was implementing this model:
http://retis.sssup.it/~tommaso/papers/rtas08.php the criticality for DEADLINE is that those tasks preempt RT99 ones, so even with controlled runtime/deadline boundaries....
* a nicer glibc wrapper, that allows me to use pthreads rather than using `syscall`: it's all pretty easy to obtain the `tid` for a calling thread (gettid), but it seems to be impossible to obtain the `tid` from `pthread_t` without some hacks which are way too dirty to share in public ...
well-known "pain" as well, thanks. T. -- Tommaso Cucinotta, Computer Engineering PhD Associate Professor at the Real-Time Systems Laboratory (ReTiS) Scuola Superiore Sant'Anna, Pisa, Italy http://retis.sssup.it/people/tommaso
