[ovs-dev] [RFC PATCH V4 8/9] netdev-dpdk: copy large packet to multi-seg. mbufs

[Kavanagh, Mark B]

>-----Original Message-----
>From: Chandran, Sugesh
>Sent: Friday, December 8, 2017 6:01 PM
>To: Kavanagh, Mark B <mark.b.kavanagh at intel.com>; dev at openvswitch.org;
>qiudayu at chinac.com
>Cc: Stokes, Ian <ian.stokes at intel.com>; Loftus, Ciara
><ciara.loftus at intel.com>; santosh.shukla at caviumnetworks.com
>Subject: RE: [ovs-dev][RFC PATCH V4 8/9] netdev-dpdk: copy large packet to
>multi-seg. mbufs
>
>
>
>Regards
>_Sugesh
>
>
>> -----Original Message-----
>> From: Kavanagh, Mark B
>> Sent: Friday, December 8, 2017 12:02 PM
>> To: dev at openvswitch.org; qiudayu at chinac.com
>> Cc: Stokes, Ian <ian.stokes at intel.com>; Loftus, Ciara
><ciara.loftus at intel.com>;
>> santosh.shukla at caviumnetworks.com; Chandran, Sugesh
>> <sugesh.chandran at intel.com>; Kavanagh, Mark B
>> <mark.b.kavanagh at intel.com>
>> Subject: [ovs-dev][RFC PATCH V4 8/9] netdev-dpdk: copy large packet to
>multi-
>> seg. mbufs
>>
>> From: Michael Qiu <qiudayu at chinac.com>
>>
>> Currently, packets are only copied to a single segment in the function
>> dpdk_do_tx_copy(). This could be an issue in the case of jumbo frames,
>> particularly when multi-segment mbufs are involved.
>>
>> This patch calculates the number of segments needed by a packet and copies
>the
>> data to each segment.
>>
>> Co-authored-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
>>
>> Signed-off-by: Michael Qiu <qiudayu at chinac.com>
>> Signed-off-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
>> ---
>>  lib/netdev-dpdk.c | 56
>> +++++++++++++++++++++++++++++++++++++++++++++++++++----
>>  1 file changed, 52 insertions(+), 4 deletions(-)
>>
>> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c index 8a81690..f83bb9e
>> 100644
>> --- a/lib/netdev-dpdk.c
>> +++ b/lib/netdev-dpdk.c
>> @@ -1830,8 +1830,10 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid,
>> struct dp_packet_batch *batch)  #endif
>>      struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
>>      struct rte_mbuf *pkts[PKT_ARRAY_SIZE];
>> +    struct rte_mbuf *temp, *head = NULL;
>>      uint32_t cnt = batch_cnt;
>>      uint32_t dropped = 0;
>> +    uint32_t i, j, nb_segs;
>[Sugesh] This function become bit longer, can we split it ?

I'll try to split out the multi-segment code into a separate function that is invoked on the basis of (nb_segs > 1).
 
>>
>>      if (dev->type != DPDK_DEV_VHOST) {
>>          /* Check if QoS has been configured for this netdev. */ @@ -1844,9
>> +1846,10 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid, struct
>> dp_packet_batch *batch)
>>
>>      uint32_t txcnt = 0;
>>
>> -    for (uint32_t i = 0; i < cnt; i++) {
>> +    for (i = 0; i < cnt; i++) {
>>          struct dp_packet *packet = batch->packets[i];
>>          uint32_t size = dp_packet_size(packet);
>> +        uint16_t max_data_len, data_len;
>>
>>          if (OVS_UNLIKELY(size > dev->max_packet_len)) {
>>              VLOG_WARN_RL(&rl, "Too big size %u max_packet_len %d", @@ -
>> 1856,15 +1859,60 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid, struct
>> dp_packet_batch *batch)
>>              continue;
>>          }
>>
>> -        pkts[txcnt] = rte_pktmbuf_alloc(dev->mp);
>> +        temp = pkts[txcnt] = rte_pktmbuf_alloc(dev->mp);
>>          if (OVS_UNLIKELY(!pkts[txcnt])) {
>>              dropped += cnt - i;
>>              break;
>>          }
>>
>> +        /* All new allocated mbuf's max data len is the same */
>> +        max_data_len = temp->buf_len - temp->data_off;
>> +
>> +        /* Calculate # of output mbufs. */
>> +        nb_segs = size / max_data_len;
>> +        if (size % max_data_len) {
>> +            nb_segs = nb_segs + 1;
>> +        }
>> +
>> +        /* Allocate additional mbufs when multiple output mbufs required.
>*/
>> +        for (j = 1; j < nb_segs; j++) {
>> +            temp->next = rte_pktmbuf_alloc(dev->mp);
>[Sugesh] Does alloc_bulk would be better to use than multiple single
>allocation from the pool?

Since we need to iterate over the set of allocated mbufs and link each to the next anyway, it's probably more straightforward with the single alloc.

>
>> +            if (!temp->next) {
>> +                rte_pktmbuf_free(pkts[txcnt]);
>
>> +                pkts[txcnt] = NULL;
>> +                break;
>> +            }
>> +            temp = temp->next;
>> +        }
>>          /* We have to do a copy for now */
>> -        memcpy(rte_pktmbuf_mtod(pkts[txcnt], void *),
>> -               dp_packet_data(packet), size);
>> +        rte_pktmbuf_pkt_len(pkts[txcnt]) = size;
>> +        temp = pkts[txcnt];
>> +
>> +        data_len = size < max_data_len ? size: max_data_len;
>> +        if (packet->source == DPBUF_DPDK) {
>> +            head = &(packet->mbuf);
>> +            while (temp && head && size > 0) {
>> +                rte_memcpy(rte_pktmbuf_mtod(temp, void *),
>> +                        dp_packet_data((struct dp_packet *)head),
>data_len);
>> +                rte_pktmbuf_data_len(temp) = data_len;
>> +                head = head->next;
>> +                size = size - data_len;
>> +                data_len =  size < max_data_len ? size: max_data_len;
>> +                temp = temp->next;
>> +            }
>> +        } else {
>> +            int offset = 0;
>> +            while (temp && size > 0) {
>> +                memcpy(rte_pktmbuf_mtod(temp, void *),
>> +                    dp_packet_at(packet, offset, data_len), data_len);
>> +                rte_pktmbuf_data_len(temp) = data_len;
>> +                temp = temp->next;
>> +                size = size - data_len;
>> +                offset += data_len;
>> +                data_len = size < max_data_len ? size: max_data_len;
>> +            }
>> +        }
>> +
>>          dp_packet_set_size((struct dp_packet *)pkts[txcnt], size);
>>          pkts[txcnt]->nb_segs = packet->mbuf.nb_segs;
>>          pkts[txcnt]->ol_flags = packet->mbuf.ol_flags;
>> --
>> 1.9.3