Hi, On 12/08/15 10:10, Michael Riesch wrote: > Hi Juri, > > On 08/11/2015 01:55 PM, Juri Lelli wrote: >> As you are running a 3.14 kernel, you probably missed this fix >> 5bfd126e80dc "sched/deadline: Fix sched_yield() behavior". Can >> you please check? > > I stumbled over this commit but somehow managed to ignore it. Anyway, I > upgraded to 4.1, now the application shows the expected behavior. > >>> As far as I understand, I have to call sched_yield() if the the >>> execution time of one loop iteration is either not constant or unknown >>> (both cases being very likely), because if I do not, a new loop >>> iteration could be started if the time budget is not empty. >>> >> >> It depends. The sched_yield() semantic for SCHED_DEADLINE might >> be used to implement some sort of reclaiming mechanism (not >> there yet) where you inform the scheduler that you are not going >> to use the remaining runtime in this period; and the scheduler >> could recycle this spare runtime for other tasks that are running >> short of it. >> >> However, I'd say that in your case you can also live without it. >> SCHED_DEADLINE can handle sporadic tasks, it depends on how you >> implement your userspace loop I guess. If you just check the active >> flag, and this flag is always set, you are right that you may >> end up executing back to back, though; in which case it seems that yield >> semantic could do the trick. > > Since samples are generated and the resulting curve looks like it was > sampled with a constant frequency, I think that sched_yield() is to be > used in this context. Before I used sched_yield(), I had to use some > sleep statements, which made the sample frequency not deterministic and > filled the CPU up. Now it seems to work pretty well. >
Great! Is there any way you can share your application sources? Maybe it is already on Github or something? I'd be really curious to have a look at it :). > Congrats on the deadline scheduler - it is a great way to introduce some > real-time capability - and thank you for your help. Sure, no problem. Thanks a lot for asking your question on the list! Best, - Juri -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
