> From: Kamalakshitha Aligeri [mailto:kamalakshitha.alig...@arm.com]
> Sent: Thursday, 9 February 2023 07.25
>
> Integrated zero-copy put API in mempool cache in i40e PMD.
> On Ampere Altra server, l3fwd single core's performance improves by 5%
> with the new API
>
> Signed-off-by: Kamalakshitha Aligeri <kamalakshitha.alig...@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com>
> Reviewed-by: Feifei Wang <feifei.wa...@arm.com>
> ---
> Link:
> https://patchwork.dpdk.org/project/dpdk/patch/20221227151700.80887-1-
> m...@smartsharesystems.com/
>
> .mailmap | 1 +
> drivers/net/i40e/i40e_rxtx_vec_common.h | 34 ++++++++++++++++++++-----
> 2 files changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/.mailmap b/.mailmap
> index 75884b6fe2..05a42edbcf 100644
> --- a/.mailmap
> +++ b/.mailmap
> @@ -670,6 +670,7 @@ Kai Ji <kai...@intel.com>
> Kaiwen Deng <kaiwenx.d...@intel.com>
> Kalesh AP <kalesh-anakkur.pura...@broadcom.com>
> Kamalakannan R <kamalakanna...@intel.com>
> +Kamalakshitha Aligeri <kamalakshitha.alig...@arm.com>
> Kamil Bednarczyk <kamil.bednarc...@intel.com>
> Kamil Chalupnik <kamilx.chalup...@intel.com>
> Kamil Rytarowski <kamil.rytarow...@caviumnetworks.com>
> diff --git a/drivers/net/i40e/i40e_rxtx_vec_common.h
> b/drivers/net/i40e/i40e_rxtx_vec_common.h
> index fe1a6ec75e..80d4a159e6 100644
> --- a/drivers/net/i40e/i40e_rxtx_vec_common.h
> +++ b/drivers/net/i40e/i40e_rxtx_vec_common.h
> @@ -95,17 +95,37 @@ i40e_tx_free_bufs(struct i40e_tx_queue *txq)
>
> n = txq->tx_rs_thresh;
>
> - /* first buffer to free from S/W ring is at index
> - * tx_next_dd - (tx_rs_thresh-1)
> - */
> + /* first buffer to free from S/W ring is at index
> + * tx_next_dd - (tx_rs_thresh-1)
> + */
> txep = &txq->sw_ring[txq->tx_next_dd - (n - 1)];
>
> if (txq->offloads & RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE) {
> - for (i = 0; i < n; i++) {
> - free[i] = txep[i].mbuf;
> - /* no need to reset txep[i].mbuf in vector path */
> + struct rte_mempool *mp = txep[0].mbuf->pool;
> + struct rte_mempool_cache *cache =
> rte_mempool_default_cache(mp, rte_lcore_id());
> +
> + if (!cache || n > RTE_MEMPOOL_CACHE_MAX_SIZE) {
If the mempool has a cache, do not compare n to RTE_MEMPOOL_CACHE_MAX_SIZE.
Instead, call rte_mempool_cache_zc_put_bulk() to determine if n is acceptable
for zero-copy.
It looks like this patch behaves incorrectly if the cache is configured to be
smaller than RTE_MEMPOOL_CACHE_MAX_SIZE. Let's say the cache size is 8, which
will make the flush threshold 12. If n is 32, your code will not enter this
branch, but proceed to call rte_mempool_cache_zc_put_bulk(), which will return
NULL, and then you will goto done.
Obviously, if there is no cache, fall back to the standard
rte_mempool_put_bulk().
> + for (i = 0; i < n ; i++)
> + free[i] = txep[i].mbuf;
> + if (!cache) {
> + rte_mempool_generic_put(mp, (void **)free, n,
> cache);
> + goto done;
> + }
> + if (n > RTE_MEMPOOL_CACHE_MAX_SIZE) {
> + rte_mempool_ops_enqueue_bulk(mp, (void **)free,
> n);
> + goto done;
> + }
> + }
> + void **cache_objs;
> +
> + cache_objs = rte_mempool_cache_zc_put_bulk(cache, mp, n);
> + if (cache_objs) {
> + for (i = 0; i < n; i++) {
> + cache_objs[i] = txep->mbuf;
> + /* no need to reset txep[i].mbuf in vector path
> */
> + txep++;
> + }
> }
> - rte_mempool_put_bulk(free[0]->pool, (void **)free, n);
> goto done;
> }
>
> --
> 2.25.1
>
