On 2019-12-29 20:45, Liron Himi wrote: > > Recently we tried to run the new l2fwd-event examples using the ‘dsw’ > as the evendev. > > We noticed that only 4096 packets were sent back to the ethdev. > > Only when we changed both ‘dequeue_depth’ and ‘enqueue_depth’ to 128 > instead of 32, it started to work. > > Do you have any objections for modifying the ‘dsw’ default > configuration to ‘128’? > I suspect the problem isn't really the default dsw burst sizes, but rather the additional requirements that dsw puts on its user. In particular, the requirement that no eventdev ports may be left "unattended".
From what I can see, l2fwd-event uses the rx ethernet adapter. In case there are no ingress packets, the rx ethernet adapter will leave its eventdev port unattended, and thus will not work properly with dsw. If someone wants to explore if this is indeed the problem, they could try adding a zero-sized rte_event_dequeue_burst() (being called for every service invocation) in the rx adapter code. A dequeue call will allow the dsw flow migration machinery to function properly, and will also periodically flush buffered events.A zero-sized enqueue operation (as suggested by the dsw documentation) would also work, but that would have the side-effect of always flushing any buffered events, which might be non-optimal from a performance point of view. The same might also hold true for the l2fwd-event code, but at least the burst-variant of the main loop will periodically attend the eventdev port (by means of a dequeue and/or enqueue). The proper way to address this issue would probably be to add a "needs maintenance" capability flag, and a pure event device maintenance function added to the eventdev API, or something along those lines. Another way might be to use a dsw-internal per lcore timer. That would instead require the user to call rte_timer_manage(). An additional complication for the latter solution is that, even though an eventdev port is not thread-safe, it doesn't really have an "owning" lcore, and thus it's difficult to figure out on which lcore to install the timer.
