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charset=us-ascii Content-Disposition: inline In-Reply-To: Hi Daniel, On 27/05/24 14:06, Daniel Bristot de Oliveira wrote: > This is v7 of Peter's SCHED_DEADLINE server infrastructure > implementation [1]. I finally managed to give this a go and can report that it works great for what I've seen. :) So, please consider this reply a Tested-by: Juri Lelli > SCHED_DEADLINE servers can help fixing starvation issues of low priority > tasks (e.g., SCHED_OTHER) when higher priority tasks monopolize CPU > cycles. Today we have RT Throttling; DEADLINE servers should be able to > replace and improve that. ... > The problem with DL server only implementation is that FIFO tasks might > suffer preemption from NORMAL even when spare CPU cycles are available. > In fact, fair deadline server is enqueued right away when NORMAL tasks > wake up and they are first scheduled by the server, thus potentially > preempting a well behaving FIFO task. This is of course not ideal. > > We had discussions about it, and one of the possibilities would be > using a different scheduling algorithm for this. But IMHO that is > an overkill. > > Juri and I discussed this and though about delaying the server > activation for the (period - runtime), thus enabling the server > only if the fair scheduler is about to starve. We called it > the defer server. > > The defer the server start to the (absolute deadline - runtime) > point in time. This is achieved by starting the dl server throttled, > with a next replenishing time set to activate the server at > (absolute deadline - runtime). > > The server is enqueued with the runtime replenished. As the fair > scheduler runs without boost, its runtime is consumed. If the > fair server has its runtime before the runtime - deadline time, > the a new period is set, and the timer armed for the new > deadline. I also wanted to pay particular attention to this part implementing the deferred server, but failed to find enough focus time for now. I will keep trying. One thing that I wondered though is if this change (and the move towards this replacing current RT throttling) would call for a Doc update. What do you think? Thanks! Juri