[ovs-dev] [PATCH v10 10/14] netdev-dpdk: copy large packet to multi-seg. mbufs

[Lam, Tiago]

On 03/10/2018 19:27, Flavio Leitner wrote:
> On Fri, Sep 28, 2018 at 05:15:11PM +0100, Tiago Lam wrote:
>> From: Mark Kavanagh <mark.b.kavanagh at intel.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.
>>
>> A new function, dpdk_buf_alloc(), has also been introduced as a wrapper
>> around the nonpmd_mp_mutex to serialise allocations from a non-pmd
>> context.
>>
>> Co-authored-by: Michael Qiu <qiudayu at chinac.com>
>> Co-authored-by: Tiago Lam <tiago.lam at intel.com>
>>
>> Signed-off-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
>> Signed-off-by: Michael Qiu <qiudayu at chinac.com>
>> Signed-off-by: Tiago Lam <tiago.lam at intel.com>
>> Acked-by: Eelco Chaudron <echaudro at redhat.com>
>> ---
>>  lib/netdev-dpdk.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++------
>>  1 file changed, 82 insertions(+), 9 deletions(-)
>>
>> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
>> index 8484239..e58e7ac 100644
>> --- a/lib/netdev-dpdk.c
>> +++ b/lib/netdev-dpdk.c
>> @@ -552,6 +552,27 @@ dpdk_rte_mzalloc(size_t sz)
>>      return rte_zmalloc(OVS_VPORT_DPDK, sz, OVS_CACHE_LINE_SIZE);
>>  }
>>  
>> +static struct rte_mbuf *
>> +dpdk_buf_alloc(struct rte_mempool *mp)
>> +{
>> +    struct rte_mbuf *mbuf = NULL;
>> +
>> +    /* If non-pmd we need to lock on nonpmd_mp_mutex mutex */
>> +    if (!dpdk_thread_is_pmd()) {
>> +        ovs_mutex_lock(&nonpmd_mp_mutex);
>> +
>> +        mbuf = rte_pktmbuf_alloc(mp);
>> +
>> +        ovs_mutex_unlock(&nonpmd_mp_mutex);
>> +
>> +        return mbuf;
>> +    }
>> +
>> +    mbuf = rte_pktmbuf_alloc(mp);
>> +
>> +    return mbuf;
>> +}
> 
> What about:
> 
>     if (dpdk_thread_is_pmd()) {
>         mbuf = rte_pktmbuf_alloc(mp);
>     } else {
>         ovs_mutex_lock(&nonpmd_mp_mutex);
> 
>         mbuf = rte_pktmbuf_alloc(mp);
> 
>         ovs_mutex_unlock(&nonpmd_mp_mutex);
>     }
> 
>     return mbuf;

It does read better. I'll use that, thanks.

Tiago.

>     
> 
> 
> 
> 
>> +
>>  void
>>  free_dpdk_buf(struct dp_packet *packet)
>>  {
>> @@ -2316,6 +2337,56 @@ out:
>>      }
>>  }
>>  
>> +static int
>> +dpdk_copy_dp_packet_to_mbuf(struct dp_packet *packet, struct rte_mbuf **head,
>> +                            struct rte_mempool *mp)
>> +{
>> +    struct rte_mbuf *mbuf, *fmbuf;
>> +    uint16_t max_data_len;
>> +    uint32_t nb_segs = 0;
>> +    uint32_t size = 0;
>> +
>> +    /* We will need the whole data for copying below */
>> +    if (!dp_packet_is_linear(packet)) {
>> +        dp_packet_linearize(packet);
>> +    }
>> +
>> +    /* Allocate first mbuf to know the size of data available */
>> +    fmbuf = mbuf = *head = dpdk_buf_alloc(mp);
>> +    if (OVS_UNLIKELY(!mbuf)) {
>> +        return ENOMEM;
>> +    }
>> +
>> +    size = dp_packet_size(packet);
>> +
>> +    /* All new allocated mbuf's max data len is the same */
>> +    max_data_len = mbuf->buf_len - mbuf->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, less the one alredy allocated above */
>> +    for (int i = 1; i < nb_segs; i++) {
>> +        mbuf->next = dpdk_buf_alloc(mp);
>> +        if (!mbuf->next) {
>> +            free_dpdk_buf(CONTAINER_OF(fmbuf, struct dp_packet, mbuf));
>> +            fmbuf = NULL;
>> +            return ENOMEM;
>> +        }
>> +        mbuf = mbuf->next;
>> +    }
>> +
>> +    fmbuf->nb_segs = nb_segs;
>> +    fmbuf->pkt_len = size;
>> +
>> +    dp_packet_mbuf_write(fmbuf, 0, size, dp_packet_data(packet));
>> +
>> +    return 0;
>> +}
>> +
>>  /* Tx function. Transmit packets indefinitely */
>>  static void
>>  dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet_batch *batch)
>> @@ -2332,6 +2403,7 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet_batch *batch)
>>      struct rte_mbuf *pkts[PKT_ARRAY_SIZE];
>>      uint32_t cnt = batch_cnt;
>>      uint32_t dropped = 0;
>> +    uint32_t i;
>>  
>>      if (dev->type != DPDK_DEV_VHOST) {
>>          /* Check if QoS has been configured for this netdev. */
>> @@ -2342,28 +2414,29 @@ 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);
>> +        int err = 0;
>>  
>>          if (OVS_UNLIKELY(size > dev->max_packet_len)) {
>>              VLOG_WARN_RL(&rl, "Too big size %u max_packet_len %d",
>>                           size, dev->max_packet_len);
>> -
>>              dropped++;
>>              continue;
>>          }
>>  
>> -        pkts[txcnt] = rte_pktmbuf_alloc(dev->dpdk_mp->mp);
>> -        if (OVS_UNLIKELY(!pkts[txcnt])) {
>> +        err = dpdk_copy_dp_packet_to_mbuf(packet, &pkts[txcnt],
>> +                                          dev->dpdk_mp->mp);
>> +        if (err != 0) {
>> +            if (err == ENOMEM) {
>> +                VLOG_ERR_RL(&rl, "Failed to alloc mbufs! %u packets dropped",
>> +                            cnt - i);
>> +            }
>> +
>>              dropped += cnt - i;
>>              break;
>>          }
>> -
>> -        /* We have to do a copy for now */
>> -        memcpy(rte_pktmbuf_mtod(pkts[txcnt], void *),
>> -               dp_packet_data(packet), size);
>> -        dp_packet_set_size((struct dp_packet *)pkts[txcnt], size);
>>          dp_packet_copy_mbuf_flags((struct dp_packet *)pkts[txcnt], packet);
>>  
>>          txcnt++;
>> -- 
>> 2.7.4
>>
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