On 1/11/21 6:39 AM, Xia, Chenbo wrote:
> 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.
The error path indeed needs some rework.
I will add a preliminary patch to rework it before this patch is
applied.
> Sorry for an extra email about this...
No worries, that's much appreciated!
Thanks,
Maxime
> 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
>
