[ovs-dev] [PATCH v8 11/13] netdev-dpdk: copy large packet to multi-seg. mbufs

Tiago Lam tiago.lam at intel.com
Mon Jun 11 16:21:28 UTC 2018


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>
---
 lib/netdev-dpdk.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 84 insertions(+), 10 deletions(-)

diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index 9b1fb9a..0079e28 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -515,6 +515,22 @@ 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)
+{
+    if (!dpdk_thread_is_pmd()) {
+        ovs_mutex_lock(&nonpmd_mp_mutex);
+    }
+
+    struct rte_mbuf *mbuf = rte_pktmbuf_alloc(mp);
+
+    if (!dpdk_thread_is_pmd()) {
+        ovs_mutex_unlock(&nonpmd_mp_mutex);
+    }
+
+    return mbuf;
+}
+
 void
 free_dpdk_buf(struct dp_packet *p)
 {
@@ -2167,6 +2183,71 @@ out:
     }
 }
 
+static int
+dpdk_prep_tx_buf(struct dp_packet *packet, struct rte_mbuf **head,
+                 struct rte_mempool *mp)
+{
+    struct rte_mbuf *temp;
+    uint32_t size = dp_packet_size(packet);
+    uint16_t max_data_len, data_len;
+    uint32_t nb_segs = 0;
+    int i;
+
+    temp = *head = dpdk_buf_alloc(mp);
+    if (OVS_UNLIKELY(!temp)) {
+        return 1;
+    }
+
+    /* 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 (i = 1; i < nb_segs; i++) {
+        temp->next = dpdk_buf_alloc(mp);
+        if (!temp->next) {
+            free_dpdk_buf((struct dp_packet *) *head);
+            *head = NULL;
+            break;
+        }
+        temp = temp->next;
+    }
+    /* We have to do a copy for now */
+    rte_pktmbuf_pkt_len(*head) = size;
+    temp = *head;
+
+    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;
+        }
+    }
+    return 0;
+}
+
 /* Tx function. Transmit packets indefinitely */
 static void
 dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet_batch *batch)
@@ -2183,6 +2264,7 @@ 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. */
@@ -2193,27 +2275,19 @@ 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);
-
         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->mp);
-        if (OVS_UNLIKELY(!pkts[txcnt])) {
+        if (dpdk_prep_tx_buf(packet, &pkts[txcnt], dev->mp)) {
             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);
 
-- 
2.7.4



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