Hi Maxime,
> -----Original Message-----
> From: Maxime Coquelin <maxime.coque...@redhat.com>
> Sent: Tuesday, December 22, 2020 12:15 AM
> To: dev@dpdk.org; Xia, Chenbo <chenbo....@intel.com>; amore...@redhat.com;
> david.march...@redhat.com; olivier.m...@6wind.com
> Cc: Maxime Coquelin <maxime.coque...@redhat.com>
> Subject: [PATCH 2/3] 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 takes uses cachelines, and
> requires alignement 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.coque...@redhat.com>
> ---
> drivers/net/virtio/virtio_ethdev.c | 10 ++++++++++
> drivers/net/virtio/virtio_rxtx.c | 8 +++-----
> drivers/net/virtio/virtio_rxtx.h | 2 +-
> 3 files changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_ethdev.c
> b/drivers/net/virtio/virtio_ethdev.c
> index 297c01a70d..a1351b36ca 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -539,6 +539,7 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t
> queue_idx)
> }
>
> if (queue_type == VTNET_RQ) {
> + struct rte_mbuf *fake_mbuf;
> size_t sz_sw = (RTE_PMD_VIRTIO_RX_MAX_BURST + vq_size) *
> sizeof(vq->sw_ring[0]);
>
> @@ -550,10 +551,18 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t
> queue_idx)
> goto fail_q_alloc;
> }
>
> + fake_mbuf = malloc(sizeof(*fake_mbuf));
> + if (!fake_mbuf) {
> + PMD_INIT_LOG(ERR, "can not allocate fake mbuf");
> + ret = -ENOMEM;
> + goto fail_q_alloc;
> + }
> +
> 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;
> @@ -636,6 +645,7 @@ virtio_free_queues(struct virtio_hw *hw)
>
> queue_type = virtio_get_queue_type(hw, i);
> if (queue_type == VTNET_RQ) {
> + free(vq->rxq.fake_mbuf);
After thinking about this again, although you add the free of fake mbuf
here, it's better to add free in virtio_init_queue too after fail_q_alloc.
And when setup_queue(hw, vq) fails, it's better to goto fail_q_alloc to
free fake mbuf. Now it will not memory leak as we use virtio_free_queues when
virtio_alloc_queues fails. But inside virtio_init_queue, it's better to
handle the errors well.. If you agree with above, it may also be good to
change the name 'fail_q_alloc' since now it may also fail when setting up
queues.
Sorry for an extra email about this...
Thanks,
Chenbo
> 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 1fcce36cbd..d147d7300a 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -703,11 +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)) {
> diff --git a/drivers/net/virtio/virtio_rxtx.h
> b/drivers/net/virtio/virtio_rxtx.h
> index 7f1036be6f..6ce5d67d15 100644
> --- 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 */
>
> --
> 2.29.2
