[dpdk-dev] [PATCH v4] net/mlx5: relaxed ordering for multi-packet RQ buffer refcnt
Honnappa Nagarahalli
Honnappa.Nagarahalli at arm.com
Thu Sep 10 03:30:39 CEST 2020
<snip>
>
> Use c11 atomics with RELAXED ordering instead of the rte_atomic ops which
> enforce unnecessary barriers on aarch64.
>
> Signed-off-by: Phil Yang <phil.yang at arm.com>
Looks good.
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
> ---
> v4:
> Remove the unnecessary ACQUIRE barrier in rx burst path. (Honnappa)
>
> v3:
> Split from the patchset:
> http://patchwork.dpdk.org/cover/68159/
>
> drivers/net/mlx5/mlx5_rxq.c | 2 +-
> drivers/net/mlx5/mlx5_rxtx.c | 16 +++++++++-------
> drivers/net/mlx5/mlx5_rxtx.h | 2 +-
> 3 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c index
> 79eb8f8..40e0239 100644
> --- a/drivers/net/mlx5/mlx5_rxq.c
> +++ b/drivers/net/mlx5/mlx5_rxq.c
> @@ -2012,7 +2012,7 @@ mlx5_mprq_buf_init(struct rte_mempool *mp,
> void *opaque_arg,
>
> memset(_m, 0, sizeof(*buf));
> buf->mp = mp;
> - rte_atomic16_set(&buf->refcnt, 1);
> + __atomic_store_n(&buf->refcnt, 1, __ATOMIC_RELAXED);
> for (j = 0; j != strd_n; ++j) {
> shinfo = &buf->shinfos[j];
> shinfo->free_cb = mlx5_mprq_buf_free_cb; diff --git
> a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c index
> 1b71e94..549477b 100644
> --- a/drivers/net/mlx5/mlx5_rxtx.c
> +++ b/drivers/net/mlx5/mlx5_rxtx.c
> @@ -1626,10 +1626,11 @@ mlx5_mprq_buf_free_cb(void *addr
> __rte_unused, void *opaque) {
> struct mlx5_mprq_buf *buf = opaque;
>
> - if (rte_atomic16_read(&buf->refcnt) == 1) {
> + if (__atomic_load_n(&buf->refcnt, __ATOMIC_RELAXED) == 1) {
> rte_mempool_put(buf->mp, buf);
> - } else if (rte_atomic16_add_return(&buf->refcnt, -1) == 0) {
> - rte_atomic16_set(&buf->refcnt, 1);
> + } else if (unlikely(__atomic_sub_fetch(&buf->refcnt, 1,
> + __ATOMIC_RELAXED) == 0)) {
> + __atomic_store_n(&buf->refcnt, 1, __ATOMIC_RELAXED);
> rte_mempool_put(buf->mp, buf);
> }
> }
> @@ -1709,7 +1710,8 @@ mlx5_rx_burst_mprq(void *dpdk_rxq, struct
> rte_mbuf **pkts, uint16_t pkts_n)
>
> if (consumed_strd == strd_n) {
> /* Replace WQE only if the buffer is still in use. */
> - if (rte_atomic16_read(&buf->refcnt) > 1) {
> + if (__atomic_load_n(&buf->refcnt,
> + __ATOMIC_RELAXED) > 1) {
> mprq_buf_replace(rxq, rq_ci & wq_mask,
> strd_n);
> /* Release the old buffer. */
> mlx5_mprq_buf_free(buf);
> @@ -1821,9 +1823,9 @@ mlx5_rx_burst_mprq(void *dpdk_rxq, struct
> rte_mbuf **pkts, uint16_t pkts_n)
> void *buf_addr;
>
> /* Increment the refcnt of the whole chunk. */
> - rte_atomic16_add_return(&buf->refcnt, 1);
> - MLX5_ASSERT((uint16_t)rte_atomic16_read(&buf-
> >refcnt) <=
> - strd_n + 1);
> + __atomic_add_fetch(&buf->refcnt, 1,
> __ATOMIC_RELAXED);
> + MLX5_ASSERT(__atomic_load_n(&buf->refcnt,
> + __ATOMIC_RELAXED) <= strd_n + 1);
> buf_addr = RTE_PTR_SUB(addr,
> RTE_PKTMBUF_HEADROOM);
> /*
> * MLX5 device doesn't use iova but it is necessary in
> a diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
> index c02a007..467f31d 100644
> --- a/drivers/net/mlx5/mlx5_rxtx.h
> +++ b/drivers/net/mlx5/mlx5_rxtx.h
> @@ -68,7 +68,7 @@ struct rxq_zip {
> /* Multi-Packet RQ buffer header. */
> struct mlx5_mprq_buf {
> struct rte_mempool *mp;
> - rte_atomic16_t refcnt; /* Atomically accessed refcnt. */
> + uint16_t refcnt; /* Atomically accessed refcnt. */
> uint8_t pad[RTE_PKTMBUF_HEADROOM]; /* Headroom for the first
> packet. */
> struct rte_mbuf_ext_shared_info shinfos[];
> /*
> --
> 2.7.4
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