On Tue, Apr 20, 2021 at 10:28:45AM +0000, Xiaoliang Yang wrote: > Hi Vladimir, > > On Tue, Apr 20, 2021 at 16:27:10AM +0800, Vladimir Oltean wrote: > > > > On Tue, Apr 20, 2021 at 03:06:40AM +0000, Xiaoliang Yang wrote: > >> Hi Vladimir. > >> > >> On Mon, Apr 19, 2021 at 20:38PM +0800, Vladimir Oltean wrote: > >> > > >> >What is a scheduled queue? When time-aware scheduling is enabled on > >> >the port, why are some queues scheduled and some not? > >> > >> The felix vsc9959 device can set SCH_TRAFFIC_QUEUES field bits to > >> define which queue is scheduled. Only the set queues serves schedule > >> traffic. In this driver we set all 8 queues to be scheduled in > >> default, so all the traffic are schedule queues to schedule queue. > > > > I understand this, what I don't really understand is the distinction > > that the switch makes between 'scheduled' and 'non-scheduled' > > traffic. What else does this distinction affect, apart from the > > guard bands added implicitly here? The tc-taprio qdisc has no notion > > of 'scheduled' queues, all queues are 'scheduled'. Do we ever need > > to set the scheduled queues mask to something other than 0xff? If > > so, when and why? > > Yes, it seems only affect the guard band. If disabling always guard > band bit, we can use SCH_TRAFFIC_QUEUES to determine which queue is > non-scheduled queue. Only the non-scheduled queue traffic will reserve > the guard band. But tc-taprio qdisc cannot set scheduled or > non-scheduled queue now. Adding this feature can be discussed in > future. > > It is not reasonable to add guardband in each queue traffic in > default, so I disable the always guard band bit for TAS config.
Ok, if true, then it makes sense to disable ALWAYS_GUARD_BAND_SCH_Q.