[dpdk-dev] [PATCH] parray: introduce internal API for dynamic arrays
Morten Brørup
mb at smartsharesystems.com
Mon Jun 21 14:10:24 CEST 2021
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Ananyev,
> Konstantin
>
> > > How can we hide the callbacks since they are used by inline burst
> functions.
> >
> > I probably I owe a better explanation to what I meant in first mail.
> > Otherwise it sounds confusing.
> > I'll try to write a more detailed one in next few days.
>
> Actually I gave it another thought over weekend, and might be we can
> hide rte_eth_dev_cb even in a simpler way. I'd use eth_rx_burst() as
> an example, but the same principle applies to other 'fast' functions.
>
> 1. Needed changes for PMDs rx_pkt_burst():
> a) change function prototype to accept 'uint16_t port_id' and
> 'uint16_t queue_id',
> instead of current 'void *'.
> b) Each PMD rx_pkt_burst() will have to call rte_eth_rx_epilog()
> function at return.
> This inline function will do all CB calls for that queue.
>
> To be more specific, let say we have some PMD: xyz with RX function:
>
> uint16_t
> xyz_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t
> nb_pkts)
> {
> struct xyz_rx_queue *rxq = rx_queue;
> uint16_t nb_rx = 0;
>
> /* do actual stuff here */
> ....
> return nb_rx;
> }
>
> It will be transformed to:
>
> uint16_t
> xyz_recv_pkts(uint16_t port_id, uint16_t queue_id, struct rte_mbuf
> **rx_pkts, uint16_t nb_pkts)
> {
> struct xyz_rx_queue *rxq;
> uint16_t nb_rx;
>
> rxq = _rte_eth_rx_prolog(port_id, queue_id);
> if (rxq == NULL)
> return 0;
> nb_rx = _xyz_real_recv_pkts(rxq, rx_pkts, nb_pkts);
> return _rte_eth_rx_epilog(port_id, queue_id, rx_pkts,
> nb_pkts);
> }
>
> And somewhere in ethdev_private.h:
>
> static inline void *
> _rte_eth_rx_prolog(uint16_t port_id, uint16_t queue_id);
> {
> struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>
> #ifdef RTE_ETHDEV_DEBUG_RX
> RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, NULL);
> RTE_FUNC_PTR_OR_ERR_RET(*dev->rx_pkt_burst, NULL);
>
> if (queue_id >= dev->data->nb_rx_queues) {
> RTE_ETHDEV_LOG(ERR, "Invalid RX queue_id=%u\n",
> queue_id);
> return NULL;
> }
> #endif
> return dev->data->rx_queues[queue_id];
> }
>
> static inline uint16_t
> _rte_eth_rx_epilog(uint16_t port_id, uint16_t queue_id, struct rte_mbuf
> **rx_pkts, const uint16_t nb_pkts);
> {
> struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>
> #ifdef RTE_ETHDEV_RXTX_CALLBACKS
> struct rte_eth_rxtx_callback *cb;
>
> /* __ATOMIC_RELEASE memory order was used when the
> * call back was inserted into the list.
> * Since there is a clear dependency between loading
> * cb and cb->fn/cb->next, __ATOMIC_ACQUIRE memory order is
> * not required.
> */
> cb = __atomic_load_n(&dev->post_rx_burst_cbs[queue_id],
> __ATOMIC_RELAXED);
>
> if (unlikely(cb != NULL)) {
> do {
> nb_rx = cb->fn.rx(port_id, queue_id, rx_pkts,
> nb_rx,
> nb_pkts, cb->param);
> cb = cb->next;
> } while (cb != NULL);
> }
> #endif
>
> rte_ethdev_trace_rx_burst(port_id, queue_id, (void **)rx_pkts,
> nb_rx);
> return nb_rx;
> }
That would make the compiler inline _rte_eth_rx_epilog() into the driver when compiling the DPDK library. But RTE_ETHDEV_RXTX_CALLBACKS is a definition for the application developer to use when compiling the DPDK application.
>
> Now, as you said above, in rte_ethdev.h we will keep only a flat array
> with pointers to 'fast' functions:
> struct {
> eth_rx_burst_t rx_pkt_burst
> eth_tx_burst_t tx_pkt_burst;
> eth_tx_prep_t tx_pkt_prepare;
> .....
> } rte_eth_dev_burst[];
>
> And rte_eth_rx_burst() will look like:
>
> static inline uint16_t
> rte_eth_rx_burst(uint16_t port_id, uint16_t queue_id,
> struct rte_mbuf **rx_pkts, const uint16_t nb_pkts)
> {
> if (port_id >= RTE_MAX_ETHPORTS)
> return 0;
> return rte_eth_dev_burst[port_id](port_id, queue_id, rx_pkts,
> nb_pkts);
> }
>
> Yes, it will require changes in *all* PMDs, but as I said before the
> changes will be a mechanic ones.
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