Re: [dpdk-dev] [PATCH v2 5/6] net/af_xdp: enable zero copy

["Mattias Rönnblom" <hofors@lysator.liu.se>]

On 2019-03-19 08:12, Xiaolong Ye wrote:
> Try to check if external mempool (from rx_queue_setup) is fit for
> af_xdp, if it is, it will be registered to af_xdp socket directly and
> there will be no packet data copy on Rx and Tx.
> 
> Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
> ---
>   drivers/net/af_xdp/rte_eth_af_xdp.c | 128 ++++++++++++++++++++--------
>   1 file changed, 91 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
> index fc60cb5c5..c22791e51 100644
> --- a/drivers/net/af_xdp/rte_eth_af_xdp.c
> +++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
> @@ -62,6 +62,7 @@ struct xsk_umem_info {
>   	struct xsk_umem *umem;
>   	struct rte_mempool *mb_pool;
>   	void *buffer;
> +	uint8_t zc;
>   };
>   
>   struct pkt_rx_queue {
> @@ -76,6 +77,7 @@ struct pkt_rx_queue {
>   
>   	struct pkt_tx_queue *pair;
>   	uint16_t queue_idx;
> +	uint8_t zc;
>   };
>   
>   struct pkt_tx_queue {
> @@ -191,17 +193,24 @@ eth_af_xdp_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>   		uint32_t len = xsk_ring_cons__rx_desc(rx, idx_rx++)->len;
>   		char *pkt = xsk_umem__get_data(rxq->umem->buffer, addr);
>   
> -		mbuf = rte_pktmbuf_alloc(rxq->mb_pool);
> -		if (mbuf) {
> -			memcpy(rte_pktmbuf_mtod(mbuf, void*), pkt, len);
> +		if (rxq->zc) {
> +			mbuf = addr_to_mbuf(rxq->umem, addr);
>   			rte_pktmbuf_pkt_len(mbuf) =
>   				rte_pktmbuf_data_len(mbuf) = len;
> -			rx_bytes += len;
>   			bufs[count++] = mbuf;
>   		} else {
> -			dropped++;
> +			mbuf = rte_pktmbuf_alloc(rxq->mb_pool);
> +			if (mbuf) {

if (likely(mbuf != NULL))

> +				memcpy(rte_pktmbuf_mtod(mbuf, void*), pkt, len);

Use rte_memcpy.

> +				rte_pktmbuf_pkt_len(mbuf) =
> +					rte_pktmbuf_data_len(mbuf) = len;
> +				rx_bytes += len;
> +				bufs[count++] = mbuf;
> +			} else {
> +				dropped++;
> +			}
> +			rte_pktmbuf_free(addr_to_mbuf(umem, addr));
>   		}
> -		rte_pktmbuf_free(addr_to_mbuf(umem, addr));
>   	}
>   
>   	xsk_ring_cons__release(rx, rcvd);
> @@ -285,22 +294,29 @@ eth_af_xdp_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>   					- ETH_AF_XDP_DATA_HEADROOM;
>   		desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx + i);
>   		mbuf = bufs[i];
> -		if (mbuf->pkt_len <= buf_len) {
> -			mbuf_to_tx = rte_pktmbuf_alloc(umem->mb_pool);
> -			if (!mbuf_to_tx) {
> -				rte_pktmbuf_free(mbuf);
> -				continue;
> -			}
> -			desc->addr = mbuf_to_addr(umem, mbuf_to_tx);
> +		if (txq->pair->zc && mbuf->pool == umem->mb_pool) {
> +			desc->addr = mbuf_to_addr(umem, mbuf);
>   			desc->len = mbuf->pkt_len;
> -			pkt = xsk_umem__get_data(umem->buffer,
> -						 desc->addr);
> -			memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
> -			       desc->len);
>   			valid++;
>   			tx_bytes += mbuf->pkt_len;
> +		} else {
> +			if (mbuf->pkt_len <= buf_len) {
> +				mbuf_to_tx = rte_pktmbuf_alloc(umem->mb_pool);
> +				if (!mbuf_to_tx) {

if (unlikely(mbuf_to_tx == NULL))

See DPDK coding conventions 1.8.1 for how to do pointer comparisons.

> +					rte_pktmbuf_free(mbuf);
> +					continue;
> +				}
> +				desc->addr = mbuf_to_addr(umem, mbuf_to_tx);
> +				desc->len = mbuf->pkt_len;
> +				pkt = xsk_umem__get_data(umem->buffer,
> +							 desc->addr);
> +				memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
> +				       desc->len);

rte_memcpy()

> +				valid++;
> +				tx_bytes += mbuf->pkt_len;
> +			}
> +			rte_pktmbuf_free(mbuf);
>   		}
> -		rte_pktmbuf_free(mbuf);
>   	}
>   
>   	xsk_ring_prod__submit(&txq->tx, nb_pkts);
> @@ -479,7 +495,7 @@ static inline uint64_t get_len(struct rte_mempool *mp)
>   	return (uint64_t)(memhdr->len);
>   }
>   
> -static struct xsk_umem_info *xdp_umem_configure(void)
> +static struct xsk_umem_info *xdp_umem_configure(struct rte_mempool *mb_pool)
>   {
>   	struct xsk_umem_info *umem;
>   	struct xsk_umem_config usr_config = {
> @@ -497,20 +513,25 @@ static struct xsk_umem_info *xdp_umem_configure(void)
>   		return NULL;
>   	}
>   
> -	snprintf(pool_name, 0x100, "af_xdp_ring");
> -	umem->mb_pool = rte_pktmbuf_pool_create_with_flags(pool_name,
> -			ETH_AF_XDP_NUM_BUFFERS,
> -			250, 0,
> -			ETH_AF_XDP_FRAME_SIZE -
> -			ETH_AF_XDP_MBUF_OVERHEAD,
> -			MEMPOOL_F_NO_SPREAD | MEMPOOL_F_PAGE_ALIGN,
> -			SOCKET_ID_ANY);
> -
> -	if (!umem->mb_pool || umem->mb_pool->nb_mem_chunks != 1) {
> -		RTE_LOG(ERR, AF_XDP,
> -			"Failed to create rte_mempool\n");
> -		goto err;
> +	if (!mb_pool) {

1.8.1

> +		snprintf(pool_name, 0x100, "af_xdp_ring");

0x100??

> +		umem->mb_pool = rte_pktmbuf_pool_create_with_flags(pool_name,
> +				ETH_AF_XDP_NUM_BUFFERS,
> +				250, 0,
> +				ETH_AF_XDP_FRAME_SIZE -
> +				ETH_AF_XDP_MBUF_OVERHEAD,
> +				MEMPOOL_F_NO_SPREAD | MEMPOOL_F_PAGE_ALIGN,
> +				SOCKET_ID_ANY);
> +
> +		if (!umem->mb_pool || umem->mb_pool->nb_mem_chunks != 1) {

1.8.1

> +			RTE_LOG(ERR, AF_XDP, "Failed to create rte_mempool\n");
> +			goto err;
> +		}
> +	} else {
> +		umem->mb_pool = mb_pool;
> +		umem->zc = 1;
>   	}
> +
>   	base_addr = (void *)get_base_addr(umem->mb_pool);
>   
>   	ret = xsk_umem__create(&umem->umem, base_addr,
> @@ -531,16 +552,43 @@ static struct xsk_umem_info *xdp_umem_configure(void)
>   	return NULL;
>   }
>   
> +static uint8_t
> +check_mempool_zc(struct rte_mempool *mp)
> +{
> +	RTE_ASSERT(mp);
> +
> +	/* must continues */
> +	if (mp->nb_mem_chunks > 1)
> +		return 0;
> +
> +	/* check header size */
> +	if (mp->header_size != RTE_CACHE_LINE_SIZE)
> +		return 0;
> +
> +	/* check base address */
> +	if ((uint64_t)get_base_addr(mp) % getpagesize() != 0)

This should be an uintptr_t cast.

> +		return 0;
> +
> +	/* check chunk size */
> +	if ((mp->elt_size + mp->header_size + mp->trailer_size) %
> +	    ETH_AF_XDP_FRAME_SIZE != 0)
> +		return 0;
> +
> +	return 1;
> +}
> +
>   static int
>   xsk_configure(struct pmd_internals *internals, struct pkt_rx_queue *rxq,
> -	      int ring_size)
> +	      int ring_size, struct rte_mempool *mb_pool)
>   {
>   	struct xsk_socket_config cfg;
>   	struct pkt_tx_queue *txq = rxq->pair;
> +	struct rte_mempool *mp;
>   	int ret = 0;
>   	int reserve_size;
>   
> -	rxq->umem = xdp_umem_configure();
> +	mp = check_mempool_zc(mb_pool) ? mb_pool : NULL;
> +	rxq->umem = xdp_umem_configure(mp);
>   	if (!rxq->umem) {
>   		ret = -ENOMEM;
>   		goto err;
> @@ -627,15 +675,21 @@ eth_rx_queue_setup(struct rte_eth_dev *dev,
>   
>   	rxq->mb_pool = mb_pool;
>   
> -	if (xsk_configure(internals, rxq, nb_rx_desc)) {
> -		RTE_LOG(ERR, AF_XDP,
> -			"Failed to configure xdp socket\n");
> +	if (xsk_configure(internals, rxq, nb_rx_desc, mb_pool)) {
> +		RTE_LOG(ERR, AF_XDP, "Failed to configure xdp socket\n");
>   		ret = -EINVAL;
>   		goto err;
>   	}
>   
>   	internals->umem = rxq->umem;
>   
> +	if (mb_pool == internals->umem->mb_pool)
> +		rxq->zc = internals->umem->zc;
> +
> +	if (rxq->zc)
> +		RTE_LOG(INFO, AF_XDP,
> +			"zero copy enabled on rx queue %d\n", rx_queue_id);
> +
>   	dev->data->rx_queues[rx_queue_id] = rxq;
>   	return 0;
>   
>