[dpdk-dev] [PATCH] parray: introduce internal API for dynamic arrays
Ananyev, Konstantin
konstantin.ananyev at intel.com
Mon Jun 21 16:38:37 CEST 2021
>
> On 6/21/2021 1:30 PM, Ananyev, Konstantin wrote:
> >
> >>
> >>> 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.
> >
> > I believe it is for both - user app and DPDK drivers.
> > AFAIK, they both have to use the same rte_config.h, otherwise things will be broken.
> > If let say RTE_ETHDEV_RXTX_CALLBACKS is not enabled in ethdev, then
> > user wouldn't be able to add a callback at first place.
> > BTW, such change will allow us to make RTE_ETHDEV_RXTX_CALLBACKS
> > internal for ethdev/PMD layer, which is a good thing from my perspective.
> >
>
> It is possible to use binary drivers (.so) as plugin. Currently application can
> decide to use or not use Rx/Tx callbacks even with binary drivers, but this
> change adds a complexity to this usecase.
Not sure I understand you here...
Can you explain a bit more what do you mean?
>
> >>
> >>>
> >>> 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.
More information about the dev
mailing list