ConnectX-4 and ConnectX-4 Lx NICs require all L2 headers of transmitted
packets to be inlined. By default only first 18 bytes are inlined,
which is insufficient if additional encapsulation is used, like Q-in-Q.
Thus, default settings caused such traffic to be dropepd on Tx.
Document a workaround to increase inlined data size in such cases.
Fixes: 505f1fe426d3 ("net/mlx5: add Tx devargs")
Cc: sta...@dpdk.org
Signed-off-by: Dmitry Kozlyuk <dkozl...@nvidia.com>
Reviewed-by: Viacheslav Ovsiienko <viachesl...@nvidia.com>
---
doc/guides/nics/mlx5.rst | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index ebefbe607e..05a89d08f2 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -705,6 +705,13 @@ Driver options
it is not recommended and may prevent NIC from sending packets over
some configurations.
+ For ConnectX-4 and ConnectX-4 Lx NICs, automatically configured value
+ is insufficient for some traffic, because they require at least all L2
headers
+ to be inlined. For example, Q-in-Q adds 4 bytes to default 18 bytes
+ of Ethernet and VLAN, thus ``txq_inline_min`` must be set to 22.
+ MPLS would add 4 bytes per label. Final value must account for all possible
+ L2 encapsulation headers used in particular environment.
+
Please, note, this minimal data inlining disengages eMPW feature (Enhanced
Multi-Packet Write), because last one does not support partial packet
inlining.
This is not very critical due to minimal data inlining is mostly required
--
2.25.1
