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

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

On 04/29/15 09:47, Vlad Zolotarov wrote:
>
>
> 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... ;)

sw_rsc_ring ;)

> 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
>