On 07/08/20 15:55, luca abeni wrote: > On Fri, 7 Aug 2020 15:43:53 +0200 > Juri Lelli <juri.lelli@xxxxxxxxxx> wrote: > > > On 07/08/20 15:28, luca abeni wrote: > > > Hi Juri, > > > > > > On Fri, 7 Aug 2020 11:56:04 +0200 > > > Juri Lelli <juri.lelli@xxxxxxxxxx> wrote: > > > > > > > Starting deadline server for lower priority classes right away > > > > when first task is enqueued might break guarantees > > > > > > Which guarantees are you thinking about, here? Response times of > > > fixed priority tasks? > > > > Response time, but also wakeup latency (which, for better or worse, is > > another important metric). > > > > > If fixed priority tasks are also scheduled through deadline servers, > > > then you can provide response-time guarantees to them even when > > > lower-priority/non-real-time tasks are scheduled through deadline > > > servers. > > > > Right, but I fear we won't be able to keep current behavior for > > wakeups: RT with highest prio always gets scheduled right away? > > Uhm... I think this depends on how the servers' parameters are > designed: assigning "wrong" (or "bad") parameters to the server used to > schedule RT tasks, this property is broken. > > (however, notice that even with the current patchset the highest > priority task might be scheduled with some delay --- if the SCHED_OTHER > deadline server is active because SCHED_OTHER tasks are being starved). But that's OK I think, because if the server is active it means that OTHER didn't get a chance to run for some time and if it continues to hung than worse problems than breaking FIFO assumptions will happen. :-/
