net/virtio: allocate fake mbuf in Rx queue

While it is worth clarifying whether the fake mbuf
in virtnet_rx struct is really necessary, it is sure
that it heavily impacts cache usage by being part of
the struct. Indeed, it uses two cachelines, and
requires alignment on a cacheline.

Before this series, it means it took 120 bytes in
virtnet_rx struct:

struct virtnet_rx {
 struct virtqueue *vq; /*0 8*/

 /* XXX 56 bytes hole, try to pack */

 /* --- cacheline 1 boundary (64 bytes) --- */
 struct rte_mbuf fake_mbuf __attribute__((__aligned__(64))); /*64 128*/
 /* --- cacheline 3 boundary (192 bytes) --- */

This patch allocates it using malloc in order to optimize
virtnet_rx cache usage and so virtqueue cache usage.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
Tested-by: Balazs Nemeth <bnemeth@redhat.com>

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index 0af16c9..090d946 100644 (file)
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -435,6 +435,7 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t queue_idx)
        int queue_type = virtio_get_queue_type(hw, queue_idx);
        int ret;
        int numa_node = dev->device->numa_node;
+       struct rte_mbuf *fake_mbuf = NULL;
 
        PMD_INIT_LOG(INFO, "setting up queue: %u on NUMA node %d",
                        queue_idx, numa_node);
@@ -550,10 +551,19 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t queue_idx)
                        goto free_hdr_mz;
                }
 
+               fake_mbuf = rte_zmalloc_socket("sw_ring", sizeof(*fake_mbuf),
+                               RTE_CACHE_LINE_SIZE, numa_node);
+               if (!fake_mbuf) {
+                       PMD_INIT_LOG(ERR, "can not allocate fake mbuf");
+                       ret = -ENOMEM;
+                       goto free_sw_ring;
+               }
+
                vq->sw_ring = sw_ring;
                rxvq = &vq->rxq;
                rxvq->port_id = dev->data->port_id;
                rxvq->mz = mz;
+               rxvq->fake_mbuf = fake_mbuf;
        } else if (queue_type == VTNET_TQ) {
                txvq = &vq->txq;
                txvq->port_id = dev->data->port_id;
@@ -612,6 +622,8 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t queue_idx)
 
 clean_vq:
        hw->cvq = NULL;
+       rte_free(fake_mbuf);
+free_sw_ring:
        rte_free(sw_ring);
 free_hdr_mz:
        rte_memzone_free(hdr_mz);
@@ -641,6 +653,7 @@ virtio_free_queues(struct virtio_hw *hw)
 
                queue_type = virtio_get_queue_type(hw, i);
                if (queue_type == VTNET_RQ) {
+                       rte_free(vq->rxq.fake_mbuf);
                        rte_free(vq->sw_ring);
                        rte_memzone_free(vq->rxq.mz);
                } else if (queue_type == VTNET_TQ) {

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 32af8d3..8df913b 100644 (file)
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -703,12 +703,9 @@ virtio_dev_rx_queue_setup_finish(struct rte_eth_dev *dev, uint16_t queue_idx)
                virtio_rxq_vec_setup(rxvq);
        }
 
-       memset(&rxvq->fake_mbuf, 0, sizeof(rxvq->fake_mbuf));
-       for (desc_idx = 0; desc_idx < RTE_PMD_VIRTIO_RX_MAX_BURST;
-            desc_idx++) {
-               vq->sw_ring[vq->vq_nentries + desc_idx] =
-                       &rxvq->fake_mbuf;
-       }
+       memset(rxvq->fake_mbuf, 0, sizeof(*rxvq->fake_mbuf));
+       for (desc_idx = 0; desc_idx < RTE_PMD_VIRTIO_RX_MAX_BURST; desc_idx++)
+               vq->sw_ring[vq->vq_nentries + desc_idx] = rxvq->fake_mbuf;
 
        if (hw->use_vec_rx && !virtio_with_packed_queue(hw)) {
                while (vq->vq_free_cnt >= RTE_VIRTIO_VPMD_RX_REARM_THRESH) {

diff --git a/drivers/net/virtio/virtio_rxtx.h b/drivers/net/virtio/virtio_rxtx.h
index 7f1036b..6ce5d67 100644 (file)
--- a/drivers/net/virtio/virtio_rxtx.h
+++ b/drivers/net/virtio/virtio_rxtx.h
@@ -19,7 +19,7 @@ struct virtnet_stats {
 
 struct virtnet_rx {
        /* dummy mbuf, for wraparound when processing RX ring. */
-       struct rte_mbuf fake_mbuf;
+       struct rte_mbuf *fake_mbuf;
        uint64_t mbuf_initializer; /**< value to init mbufs. */
        struct rte_mempool *mpool; /**< mempool for mbuf allocation */