> > + OVS AF_XDP netdev is using the userspace datapath, the same datapath
> > + as used by OVS-DPDK. So it requires --disable-system for ovs-vswitchd
> > + and datapath_type=netdev when adding a new bridge.
>
> I don't think that '--disable-system' is needed. It doesn't affect anything.
>
Thanks I will remove it.
> <snip>
>
> > +int
> > +netdev_linux_afxdp_batch_send(struct xsk_socket_info *xsk,
> > + struct dp_packet_batch *batch)
> > +{
>
> One important issue here. netdev_linux_send() is thread-safe, because
> all the syscalls and memory allocations there are thread-safe.
> However, all the xsk_ring_* APIs are not thread safe and if two
> threads will try to send packets to the same tx queue they might
> destroy the rings. So, it's necessary to start using 'concurrent_txq'
> flag with per-queue locks.
> Note that 'concurrent_txq' == 'false' only if 'n_txq' > 'n_pmd_threads'.
>
Thanks!
I have one question. For example if I have n_txq=4 and n_pmd_threds=2,
then concurrent_txq = false.
Assume pmd1 processing rx queue0 on port1 and pmd2 processes rx queue0 on port2.
What if both pmd1 and pmd2 try to send AF_XDP packet tx queue0 on port2?
Then both pmd threads are calling the send function on port2 queue0
concurrently.
Does that mean I have to unconditionally add per-queue lock?
Regards,
William
> > + struct umem_elem *elems_pop[BATCH_SIZE];
> > + struct umem_elem *elems_push[BATCH_SIZE];
> > + uint32_t tx_done, idx_cq = 0;
> > + struct dp_packet *packet;
> > + uint32_t idx = 0;
> > + int j, ret, retry_count = 0;
> > + const int max_retry = 4;
> > +
> > + ret = umem_elem_pop_n(&xsk->umem->mpool, batch->count, (void
> > **)elems_pop);
> > + if (OVS_UNLIKELY(ret)) {
> > + return EAGAIN;
> > + }
> > +
> > + /* Make sure we have enough TX descs */
> > + ret = xsk_ring_prod__reserve(&xsk->tx, batch->count, &idx);
> > + if (OVS_UNLIKELY(ret == 0)) {
> > + umem_elem_push_n(&xsk->umem->mpool, batch->count, (void
> > **)elems_pop);
> > + return EAGAIN;
> > + }
> > +
> > + DP_PACKET_BATCH_FOR_EACH (i, packet, batch) {
> > + struct umem_elem *elem;
> > + uint64_t index;
> > +
> > + elem = elems_pop[i];
> > + /* Copy the packet to the umem we just pop from umem pool.
> > + * We can avoid this copy if the packet and the pop umem
> > + * are located in the same umem.
> > + */
> > + memcpy(elem, dp_packet_data(packet), dp_packet_size(packet));
> > +
> > + index = (uint64_t)((char *)elem - (char *)xsk->umem->buffer);
> > + xsk_ring_prod__tx_desc(&xsk->tx, idx + i)->addr = index;
> > + xsk_ring_prod__tx_desc(&xsk->tx, idx + i)->len
> > + = dp_packet_size(packet);
> > + }
> > + xsk_ring_prod__submit(&xsk->tx, batch->count);
> > + xsk->outstanding_tx += batch->count;
> > +
> > + ret = kick_tx(xsk);
> > + if (OVS_UNLIKELY(ret)) {
> > + umem_elem_push_n(&xsk->umem->mpool, batch->count, (void
> > **)elems_pop);
> > + VLOG_WARN_RL(&rl, "error sending AF_XDP packet: %s",
> > + ovs_strerror(ret));
> > + return ret;
> > + }
> > +
> > +retry:
> > + /* Process CQ */
> > + tx_done = xsk_ring_cons__peek(&xsk->umem->cq, batch->count, &idx_cq);
> > + if (tx_done > 0) {
> > + xsk->outstanding_tx -= tx_done;
> > + xsk->tx_npkts += tx_done;
> > + }
> > +
> > + /* Recycle back to umem pool */
> > + for (j = 0; j < tx_done; j++) {
> > + struct umem_elem *elem;
> > + uint64_t addr;
> > +
> > + addr = *xsk_ring_cons__comp_addr(&xsk->umem->cq, idx_cq++);
> > +
> > + elem = ALIGNED_CAST(struct umem_elem *,
> > + (char *)xsk->umem->buffer + addr);
> > + elems_push[j] = elem;
> > + }
> > +
> > + ret = umem_elem_push_n(&xsk->umem->mpool, tx_done, (void
> > **)elems_push);
> > + ovs_assert(ret == 0);
> > +
> > + xsk_ring_cons__release(&xsk->umem->cq, tx_done);
> > +
> > + if (xsk->outstanding_tx > PROD_NUM_DESCS - (PROD_NUM_DESCS >> 2)) {
> > + /* If there are still a lot not transmitted, try harder. */
> > + if (retry_count++ > max_retry) {
> > + return 0;
> > + }
> > + goto retry;
> > + }
> > +
> > + return 0;
> > +}
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