Re: [dpdk-dev] [PATCH v1 3/4] ixgbe: Kill ixgbe_recv_scattered_pkts()

[Vlad Zolotarov <vladz@cloudius-systems.com>]

On 04/28/15 20:42, Ananyev, Konstantin wrote:
> Hi Vlad,
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Vlad Zolotarov
>> Sent: Sunday, April 26, 2015 3:46 PM
>> To: dev@dpdk.org
>> Subject: [dpdk-dev] [PATCH v1 3/4] ixgbe: Kill ixgbe_recv_scattered_pkts()
>>
>> Kill ixgbe_recv_scattered_pkts() - use ixgbe_recv_pkts_lro_single_alloc()
>> instead.
>>
>> Work against HW queues in LRO and scattered Rx cases is exactly the same.
>> Therefore we may drop the inferior callback.
>>
>> Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
>> ---
>>   lib/librte_pmd_ixgbe/ixgbe_ethdev.c |   2 +-
>>   lib/librte_pmd_ixgbe/ixgbe_ethdev.h |   3 -
>>   lib/librte_pmd_ixgbe/ixgbe_rxtx.c   | 243 +-----------------------------------
>>   3 files changed, 7 insertions(+), 241 deletions(-)
>>
>> diff --git a/lib/librte_pmd_ixgbe/ixgbe_ethdev.c b/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
>> index aec1de9..5f9a1cf 100644
>> --- a/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
>> +++ b/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
>> @@ -986,7 +986,7 @@ eth_ixgbevf_dev_init(struct rte_eth_dev *eth_dev)
>>   	 * RX function */
>>   	if (rte_eal_process_type() != RTE_PROC_PRIMARY){
>>   		if (eth_dev->data->scattered_rx)
>> -			eth_dev->rx_pkt_burst = ixgbe_recv_scattered_pkts;
>> +			eth_dev->rx_pkt_burst = ixgbe_recv_pkts_lro_single_alloc;
>>   		return 0;
>>   	}
>>
>> diff --git a/lib/librte_pmd_ixgbe/ixgbe_ethdev.h b/lib/librte_pmd_ixgbe/ixgbe_ethdev.h
>> index 5b90115..419ea5d 100644
>> --- a/lib/librte_pmd_ixgbe/ixgbe_ethdev.h
>> +++ b/lib/librte_pmd_ixgbe/ixgbe_ethdev.h
>> @@ -352,9 +352,6 @@ void ixgbevf_dev_rxtx_start(struct rte_eth_dev *dev);
>>   uint16_t ixgbe_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
>>   		uint16_t nb_pkts);
>>
>> -uint16_t ixgbe_recv_scattered_pkts(void *rx_queue,
>> -		struct rte_mbuf **rx_pkts, uint16_t nb_pkts);
>> -
>>   uint16_t ixgbe_recv_pkts_lro_single_alloc(void *rx_queue,
>>   		struct rte_mbuf **rx_pkts, uint16_t nb_pkts);
>>   uint16_t ixgbe_recv_pkts_lro_bulk_alloc(void *rx_queue,
>> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
>> index a45f51e..c23e20f 100644
>> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
>> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
>> @@ -1722,239 +1722,6 @@ ixgbe_recv_pkts_lro_bulk_alloc(void *rx_queue, struct rte_mbuf **rx_pkts,
>>   	return ixgbe_recv_pkts_lro(rx_queue, rx_pkts, nb_pkts, true);
>>   }
>>
>> -uint16_t
>> -ixgbe_recv_scattered_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
>> -			  uint16_t nb_pkts)
>> -{
>> -	struct ixgbe_rx_queue *rxq;
>> -	volatile union ixgbe_adv_rx_desc *rx_ring;
>> -	volatile union ixgbe_adv_rx_desc *rxdp;
>> -	struct ixgbe_rx_entry *sw_ring;
>> -	struct ixgbe_rx_entry *rxe;
>> -	struct rte_mbuf *first_seg;
>> -	struct rte_mbuf *last_seg;
>> -	struct rte_mbuf *rxm;
>> -	struct rte_mbuf *nmb;
>> -	union ixgbe_adv_rx_desc rxd;
>> -	uint64_t dma; /* Physical address of mbuf data buffer */
>> -	uint32_t staterr;
>> -	uint16_t rx_id;
>> -	uint16_t nb_rx;
>> -	uint16_t nb_hold;
>> -	uint16_t data_len;
>> -
>> -	nb_rx = 0;
>> -	nb_hold = 0;
>> -	rxq = rx_queue;
>> -	rx_id = rxq->rx_tail;
>> -	rx_ring = rxq->rx_ring;
>> -	sw_ring = rxq->sw_ring;
>> -
>> -	/*
>> -	 * Retrieve RX context of current packet, if any.
>> -	 */
>> -	first_seg = rxq->pkt_first_seg;
>> -	last_seg = rxq->pkt_last_seg;
>> -
>> -	while (nb_rx < nb_pkts) {
>> -	next_desc:
>> -		/*
>> -		 * The order of operations here is important as the DD status
>> -		 * bit must not be read after any other descriptor fields.
>> -		 * rx_ring and rxdp are pointing to volatile data so the order
>> -		 * of accesses cannot be reordered by the compiler. If they were
>> -		 * not volatile, they could be reordered which could lead to
>> -		 * using invalid descriptor fields when read from rxd.
>> -		 */
>> -		rxdp = &rx_ring[rx_id];
>> -		staterr = rxdp->wb.upper.status_error;
>> -		if (! (staterr & rte_cpu_to_le_32(IXGBE_RXDADV_STAT_DD)))
>> -			break;
>> -		rxd = *rxdp;
>> -
>> -		/*
>> -		 * Descriptor done.
>> -		 *
>> -		 * Allocate a new mbuf to replenish the RX ring descriptor.
>> -		 * If the allocation fails:
>> -		 *    - arrange for that RX descriptor to be the first one
>> -		 *      being parsed the next time the receive function is
>> -		 *      invoked [on the same queue].
>> -		 *
>> -		 *    - Stop parsing the RX ring and return immediately.
>> -		 *
>> -		 * This policy does not drop the packet received in the RX
>> -		 * descriptor for which the allocation of a new mbuf failed.
>> -		 * Thus, it allows that packet to be later retrieved if
>> -		 * mbuf have been freed in the mean time.
>> -		 * As a side effect, holding RX descriptors instead of
>> -		 * systematically giving them back to the NIC may lead to
>> -		 * RX ring exhaustion situations.
>> -		 * However, the NIC can gracefully prevent such situations
>> -		 * to happen by sending specific "back-pressure" flow control
>> -		 * frames to its peer(s).
>> -		 */
>> -		PMD_RX_LOG(DEBUG, "port_id=%u queue_id=%u rx_id=%u "
>> -			   "staterr=0x%x data_len=%u",
>> -			   (unsigned) rxq->port_id, (unsigned) rxq->queue_id,
>> -			   (unsigned) rx_id, (unsigned) staterr,
>> -			   (unsigned) rte_le_to_cpu_16(rxd.wb.upper.length));
>> -
>> -		nmb = rte_rxmbuf_alloc(rxq->mb_pool);
>> -		if (nmb == NULL) {
>> -			PMD_RX_LOG(DEBUG, "RX mbuf alloc failed port_id=%u "
>> -				   "queue_id=%u", (unsigned) rxq->port_id,
>> -				   (unsigned) rxq->queue_id);
>> -			rte_eth_devices[rxq->port_id].data->rx_mbuf_alloc_failed++;
>> -			break;
>> -		}
>> -
>> -		nb_hold++;
>> -		rxe = &sw_ring[rx_id];
>> -		rx_id++;
>> -		if (rx_id == rxq->nb_rx_desc)
>> -			rx_id = 0;
>> -
>> -		/* Prefetch next mbuf while processing current one. */
>> -		rte_ixgbe_prefetch(sw_ring[rx_id].mbuf);
>> -
>> -		/*
>> -		 * When next RX descriptor is on a cache-line boundary,
>> -		 * prefetch the next 4 RX descriptors and the next 8 pointers
>> -		 * to mbufs.
>> -		 */
>> -		if ((rx_id & 0x3) == 0) {
>> -			rte_ixgbe_prefetch(&rx_ring[rx_id]);
>> -			rte_ixgbe_prefetch(&sw_ring[rx_id]);
>> -		}
>> -
>> -		/*
>> -		 * Update RX descriptor with the physical address of the new
>> -		 * data buffer of the new allocated mbuf.
>> -		 */
>> -		rxm = rxe->mbuf;
>> -		rxe->mbuf = nmb;
>> -		dma = rte_cpu_to_le_64(RTE_MBUF_DATA_DMA_ADDR_DEFAULT(nmb));
>> -		rxdp->read.hdr_addr = dma;
>> -		rxdp->read.pkt_addr = dma;
>> -
>> -		/*
>> -		 * Set data length & data buffer address of mbuf.
>> -		 */
>> -		data_len = rte_le_to_cpu_16(rxd.wb.upper.length);
>> -		rxm->data_len = data_len;
>> -		rxm->data_off = RTE_PKTMBUF_HEADROOM;
>> -
>> -		/*
>> -		 * If this is the first buffer of the received packet,
>> -		 * set the pointer to the first mbuf of the packet and
>> -		 * initialize its context.
>> -		 * Otherwise, update the total length and the number of segments
>> -		 * of the current scattered packet, and update the pointer to
>> -		 * the last mbuf of the current packet.
>> -		 */
>> -		if (first_seg == NULL) {
>> -			first_seg = rxm;
>> -			first_seg->pkt_len = data_len;
>> -			first_seg->nb_segs = 1;
>> -		} else {
>> -			first_seg->pkt_len = (uint16_t)(first_seg->pkt_len
>> -					+ data_len);
>> -			first_seg->nb_segs++;
>> -			last_seg->next = rxm;
>> -		}
>> -
>> -		/*
>> -		 * If this is not the last buffer of the received packet,
>> -		 * update the pointer to the last mbuf of the current scattered
>> -		 * packet and continue to parse the RX ring.
>> -		 */
>> -		if (! (staterr & IXGBE_RXDADV_STAT_EOP)) {
>> -			last_seg = rxm;
>> -			goto next_desc;
>> -		}
>> -
>> -		/*
>> -		 * This is the last buffer of the received packet.
>> -		 * If the CRC is not stripped by the hardware:
>> -		 *   - Subtract the CRC	length from the total packet length.
>> -		 *   - If the last buffer only contains the whole CRC or a part
>> -		 *     of it, free the mbuf associated to the last buffer.
>> -		 *     If part of the CRC is also contained in the previous
>> -		 *     mbuf, subtract the length of that CRC part from the
>> -		 *     data length of the previous mbuf.
>> -		 */
>> -		rxm->next = NULL;
>> -		if (unlikely(rxq->crc_len > 0)) {
>> -			first_seg->pkt_len -= ETHER_CRC_LEN;
>> -			if (data_len <= ETHER_CRC_LEN) {
>> -				rte_pktmbuf_free_seg(rxm);
>> -				first_seg->nb_segs--;
>> -				last_seg->data_len = (uint16_t)
>> -					(last_seg->data_len -
>> -					 (ETHER_CRC_LEN - data_len));
>> -				last_seg->next = NULL;
>> -			} else
>> -				rxm->data_len =
>> -					(uint16_t) (data_len - ETHER_CRC_LEN);
>> -		}
>> -
>> -		/* Initialize the first mbuf of the returned packet */
>> -		ixgbe_fill_cluster_head_buf(first_seg, &rxd, rxq->port_id,
>> -					    staterr);
>> -
>> -		/* Prefetch data of first segment, if configured to do so. */
>> -		rte_packet_prefetch((char *)first_seg->buf_addr +
>> -			first_seg->data_off);
>> -
>> -		/*
>> -		 * Store the mbuf address into the next entry of the array
>> -		 * of returned packets.
>> -		 */
>> -		rx_pkts[nb_rx++] = first_seg;
>> -
>> -		/*
>> -		 * Setup receipt context for a new packet.
>> -		 */
>> -		first_seg = NULL;
>> -	}
>> -
>> -	/*
>> -	 * Record index of the next RX descriptor to probe.
>> -	 */
>> -	rxq->rx_tail = rx_id;
>> -
>> -	/*
>> -	 * Save receive context.
>> -	 */
>> -	rxq->pkt_first_seg = first_seg;
>> -	rxq->pkt_last_seg = last_seg;
>> -
>> -	/*
>> -	 * If the number of free RX descriptors is greater than the RX free
>> -	 * threshold of the queue, advance the Receive Descriptor Tail (RDT)
>> -	 * register.
>> -	 * Update the RDT with the value of the last processed RX descriptor
>> -	 * minus 1, to guarantee that the RDT register is never equal to the
>> -	 * RDH register, which creates a "full" ring situtation from the
>> -	 * hardware point of view...
>> -	 */
>> -	nb_hold = (uint16_t) (nb_hold + rxq->nb_rx_hold);
>> -	if (nb_hold > rxq->rx_free_thresh) {
>> -		PMD_RX_LOG(DEBUG, "port_id=%u queue_id=%u rx_tail=%u "
>> -			   "nb_hold=%u nb_rx=%u",
>> -			   (unsigned) rxq->port_id, (unsigned) rxq->queue_id,
>> -			   (unsigned) rx_id, (unsigned) nb_hold,
>> -			   (unsigned) nb_rx);
>> -		rx_id = (uint16_t) ((rx_id == 0) ?
>> -				     (rxq->nb_rx_desc - 1) : (rx_id - 1));
>> -		IXGBE_PCI_REG_WRITE(rxq->rdt_reg_addr, rx_id);
>> -		nb_hold = 0;
>> -	}
>> -	rxq->nb_rx_hold = nb_hold;
>> -	return (nb_rx);
>> -}
>> -
>>   /*********************************************************************
>>    *
>>    *  Queue management functions
>> @@ -2623,7 +2390,7 @@ ixgbe_dev_rx_queue_setup(struct rte_eth_dev *dev,
>>   		return (-ENOMEM);
>>   	}
>>
>> -	if (rsc_requested) {
>> +	if (rsc_requested || dev_rx_mode->enable_scatter) {
>>   		rxq->sw_rsc_ring =
>>   			rte_zmalloc_socket("rxq->sw_rsc_ring",
>>   					   sizeof(struct ixgbe_rsc_entry) * len,
> I think here is a problem:
> We allocate sw_rsc_ring only if user explicitly requested LRO or scattered rx.
> Though later, ixgbe_dev_rx_init() might implicitly enable scattered rx, if the provided mbufs are too small:
>
> buf_size = (uint16_t) ((srrctl & IXGBE_SRRCTL_BSIZEPKT_MASK) <<
>                                         IXGBE_SRRCTL_BSIZEPKT_SHIFT);
>
>   /* It adds dual VLAN length for supporting dual VLAN */
>   if (dev->data->dev_conf.rxmode.max_rx_pkt_len +
>                                             2 * IXGBE_VLAN_TAG_SIZE > buf_size)
> dev->data->scattered_rx = 1;
>
> So, ixgbe_recv_pkts_lro_*_alloc() will be selected, but ixgbe_recv_pkts_lro will be 0.

U meant "sw_ring will be NULL" I guess... ;) Yeah, u are right. Missed that.

>
> Probably the easiest and safest fix, is to always allocate sw_rsc_ring for the queue.
> After all, it would consume at max a bit more than 32KB - doesn't seem that much to me.

I agree. I should have dropped this conditioning...
Sending the v2... ;)

> Konstantin
>
>> @@ -4017,12 +3784,13 @@ void ixgbe_set_rx_function(struct rte_eth_dev *dev)
>>
>>   			dev->rx_pkt_burst = ixgbe_recv_scattered_pkts_vec;
>>   		} else {
>> -			PMD_INIT_LOG(DEBUG, "Using Regualr (non-vector) "
>> +			PMD_INIT_LOG(DEBUG, "Using Regualr (non-vector, "
>> +					    "single allocation) "
>>   					    "Scattered Rx callback "
>>   					    "(port=%d).",
>>   				     dev->data->port_id);
>>
>> -			dev->rx_pkt_burst = ixgbe_recv_scattered_pkts;
>> +			dev->rx_pkt_burst = ixgbe_recv_pkts_lro_single_alloc;
>>   		}
>>   	/*
>>   	 * Below we set "simple" callbacks according to port/queues parameters.
>> @@ -4855,7 +4623,8 @@ ixgbevf_dev_rx_init(struct rte_eth_dev *dev)
>>   					ixgbe_recv_scattered_pkts_vec;
>>   			else
>>   #endif
>> -				dev->rx_pkt_burst = ixgbe_recv_scattered_pkts;
>> +				dev->rx_pkt_burst =
>> +					ixgbe_recv_pkts_lro_single_alloc;
>>   		}
>>   	}
>>
>> --
>> 2.1.0