[dpdk-dev] [PATCH] doc: inline data settings affect mlx5 Tx queue max size

Viacheslav Ovsiienko viacheslavo at mellanox.com
Thu Aug 8 13:47:23 CEST 2019

Introduces the possible limitations on maximal Tx queue
size in descriptors if Tx inline data are enabled.

Signed-off-by: Viacheslav Ovsiienko <viacheslavo at mellanox.com>
 doc/guides/nics/mlx5.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index d6082ac..72de5e6 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -162,6 +162,12 @@ Limitations
   To receive IPv6 Multicast messages on VM, explicitly set the relevant
   MAC address using rte_eth_dev_mac_addr_add() API.
+- the amount of descriptors in Tx queue may be limited by data inline settings.
+  Inline data require the more descriptor building blocks and overall block
+  amount may exceed the hardware supported limits. The application should
+  reduce the requested Tx size or adjust data inline settings with
+  ``txq_inline_max`` and ``txq_inline_mpw`` devarg keys.
 - E-Switch decapsulation Flow:
   - can be applied to PF port only.
@@ -400,6 +406,10 @@ Run-time configuration
   option should be used with care, as it may lower performance when back
   pressure is not expected.
+  If inline data are enabled it may affect the maximal size of Tx queue in
+  descriptors because the inline data increase the descriptor size and
+  queue size limits supported by hardware may be exceeded.
 - ``txq_inline_min`` parameter [int]
   Minimal amount of data to be inlined into WQE during Tx operations. NICs

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