Andrew, Ferruh, Thomas, which behavior does ethdev assume (see below)?
> This patch was created with the assumption > that stopped queues may not be used for Rx/Tx. > No-op behavior of rte_eth_rx/tx_burst() > for a stopped queue is not documented. > Yes, at least some PMDs implement it this way. > But is this behavior intended? > > It is the application that stops the queue or starts it deferred. > Stopping is non-atomic, so polling the queue is not allowed during it. > Hence, if the application intends to stop queues, it must either: > > a) Know the queue is not polled before stopping it. > Use case: a secondary that was polling the queue has crashed, > the primary is doing a recovery to free all mbufs. > There is no issue since there is no poller to touch the queue. > > b) Tell the poller to skip the queue for the time of stopping it. > Use case: deferred queue start or queue reconfiguration. > But if the poller is cooperating anyway, > what prevents it from not touching the queue for longer? > > The same considerations apply to starting a queue. > > No-op behavior is convenient from the application point of view. > But it also means that pollers of stopped queues > will go all the way down to PMD Rx/Tx routines, wasting cycles, > and some PMDs will do a check for the queue state, > even though it may never be needed for a particular application.
