On 5/7/2021 10:26 AM, David Marchand wrote:

On Wed, Apr 28, 2021 at 9:21 AM Min Hu (Connor) [off-list ref] wrote:

quoted

From: Chengchang Tang <tangchengchang@huawei.com>

Tx prepare should be called only when necessary to reduce the impact on
performance.

For partial TX offload, users need to call rte_eth_tx_prepare() to invoke
the tx_prepare callback of PMDs. In this callback, the PMDs adjust the
packet based on the offloading used by the user. (e.g. For some PMDs,
pseudo-headers need to be calculated when the TX cksum is offloaded.)

However, for the users, they cannot grasp all the hardware and PMDs
characteristics. As a result, users cannot decide when they need to
actually call tx_prepare. Therefore, we should assume that the user calls
rte_eth_tx_prepare() when using any Tx offloading to ensure that related
functions work properly. Whether packets need to be adjusted should be
determined by PMDs. They can make judgments in the dev_configure or
queue_setup phase. When the related function is not used, the pointer of
tx_prepare should be set to NULL to reduce the performance loss caused by
invoking rte_eth_tx_repare().

In this patch, if tx_prepare is not required for the offloading used by
the users, the tx_prepare pointer will be set to NULL.

Fixes: bba636698316 ("net/hns3: support Rx/Tx and related operations")
Cc: stable@dpdk.org

Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
Signed-off-by: Min Hu (Connor) <redacted>
---
 drivers/net/hns3/hns3_rxtx.c | 36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hns3/hns3_rxtx.c b/drivers/net/hns3/hns3_rxtx.c
index 3881a72..7ac3a48 100644
--- a/drivers/net/hns3/hns3_rxtx.c
+++ b/drivers/net/hns3/hns3_rxtx.c

@@ -4203,17 +4203,45 @@ hns3_tx_check_simple_support(struct rte_eth_dev *dev)
        return (offloads == (offloads & DEV_TX_OFFLOAD_MBUF_FAST_FREE));
 }

+static bool
+hns3_get_tx_prep_needed(struct rte_eth_dev *dev)
+{
+#ifdef RTE_LIBRTE_ETHDEV_DEBUG
+       /* always perform tx_prepare when debug */
+       return true;

dev is unused in this case.
http://mails.dpdk.org/archives/test-report/2021-May/193391.html

Thanks David,

@Connor, can you please send a quick fix for it?
'RTE_SET_USED(dev);' should fix it.