On 5/23/2024 5:26 PM, Konstantin Ananyev wrote:
> From: Konstantin Ananyev <konstantin.anan...@huawei.com>
>
> ../drivers/net/ice/ice_rxtx.c:1871:29: warning: variable length array used
> [-Wvla]
>
> Here VLA is used as a temp array for mbufs that will be used as a split
> RX data buffers.
> As at any given time only one thread can do RX from particular queue,
> at rx_queue_setup() we can allocate extra space for that array, and then
> safely use it at RX fast-path.
>
Is there a reason to allocate extra space in sw_ring and used some part
of it for split buffer, instead of allocating a new buffer for it?
> Signed-off-by: Konstantin Ananyev <konstantin.anan...@huawei.com>
> ---
> drivers/net/ice/ice_rxtx.c | 18 ++++++++++++------
> drivers/net/ice/ice_rxtx.h | 2 ++
> 2 files changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ice/ice_rxtx.c b/drivers/net/ice/ice_rxtx.c
> index 95a2db3432..6395a3b50a 100644
> --- a/drivers/net/ice/ice_rxtx.c
> +++ b/drivers/net/ice/ice_rxtx.c
> @@ -1171,7 +1171,7 @@ ice_rx_queue_setup(struct rte_eth_dev *dev,
> struct ice_vsi *vsi = pf->main_vsi;
> struct ice_rx_queue *rxq;
> const struct rte_memzone *rz;
> - uint32_t ring_size;
> + uint32_t ring_size, tlen;
> uint16_t len;
> int use_def_burst_func = 1;
> uint64_t offloads;
> @@ -1279,9 +1279,14 @@ ice_rx_queue_setup(struct rte_eth_dev *dev,
> /* always reserve more for bulk alloc */
> len = (uint16_t)(nb_desc + ICE_RX_MAX_BURST);
>
> + /* allocate extra entries for SW split buffer */
> + tlen = ((rxq->offloads & RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT) != 0) ?
> + rxq->rx_free_thresh : 0;
> + tlen += len;
> +
> /* Allocate the software ring. */
> rxq->sw_ring = rte_zmalloc_socket(NULL,
> - sizeof(struct ice_rx_entry) * len,
> + sizeof(struct ice_rx_entry) * tlen,
> RTE_CACHE_LINE_SIZE,
> socket_id);
> if (!rxq->sw_ring) {
> @@ -1290,6 +1295,8 @@ ice_rx_queue_setup(struct rte_eth_dev *dev,
> return -ENOMEM;
> }
>
> + rxq->sw_split_buf = (tlen == len) ? NULL : rxq->sw_ring + len;
> +
> ice_reset_rx_queue(rxq);
> rxq->q_set = true;
> dev->data->rx_queues[queue_idx] = rxq;
> @@ -1868,7 +1875,6 @@ ice_rx_alloc_bufs(struct ice_rx_queue *rxq)
> uint64_t dma_addr;
> int diag, diag_pay;
> uint64_t pay_addr;
> - struct rte_mbuf *mbufs_pay[rxq->rx_free_thresh];
>
> /* Allocate buffers in bulk */
> alloc_idx = (uint16_t)(rxq->rx_free_trigger -
> @@ -1883,7 +1889,7 @@ ice_rx_alloc_bufs(struct ice_rx_queue *rxq)
>
> if (rxq->offloads & RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT) {
> diag_pay = rte_mempool_get_bulk(rxq->rxseg[1].mp,
> - (void *)mbufs_pay, rxq->rx_free_thresh);
> + (void *)rxq->sw_split_buf, rxq->rx_free_thresh);
>
Are we allowed to call 'rte_mempool_get_bulk()' with NULL object_table,
as 'rxq->sw_split_buf' can be NULL?
Perhaps can allocate 'rxq->sw_split_buf' even buffer split offload is
not enabled?
