[dpdk-dev] [PATCH] doc: update inline settings in mlx5 guide
viacheslavo at mellanox.com
Wed Aug 7 14:57:47 CEST 2019
This patch updates mlx5 documentation in parts:
- txq_inline_min parameter is described in more details,
values are fixed
- maximal amount of segments in multi-segment packets.
Signed-off-by: Viacheslav Ovsiienko <viacheslavo at mellanox.com>
doc/guides/nics/mlx5.rst | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)
diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index f7a076f..d6082ac 100644
@@ -124,9 +124,10 @@ Limitations
Will match any ipv4 packet (VLAN included).
-- A multi segment packet must have less than 6 segments in case the Tx burst function
- is set to multi-packet send or Enhanced multi-packet send. Otherwise it must have
- less than 50 segments.
+- A multi segment packet must have not more segments than reported by dev_infos_get()
+ in tx_desc_lim.nb_seg_max field. This value depends on maximal supported Tx descriptor
+ size and ``txq_inline_min`` settings and may be from 2 (worst case forced by maximal
+ inline settings) to 58.
- Flows with a VXLAN Network Identifier equal (or ends to be equal)
to 0 are not supported.
@@ -403,25 +404,31 @@ Run-time configuration
Minimal amount of data to be inlined into WQE during Tx operations. NICs
may require this minimal data amount to operate correctly. The exact value
- may depend on NIC operation mode, requested offloads, etc.
+ may depend on NIC operation mode, requested offloads, etc. It is strongly
+ recommended to omit this parameter and use the default values. Anyway,
+ applications using this parameter should take into consideration that
+ specifying an inconsistent value may prevent the NIC from sending packets.
If ``txq_inline_min`` key is present the specified value (may be aligned
by the driver in order not to exceed the limits and provide better descriptor
- space utilization) will be used by the driver and it is guaranteed the
- requested data bytes are inlined into the WQE beside other inline settings.
- This keys also may update ``txq_inline_max`` value (default of specified
- explicitly in devargs) to reserve the space for inline data.
+ space utilization) will be used by the driver and it is guaranteed that
+ requested amount of data bytes are inlined into the WQE beside other inline
+ settings. This key also may update ``txq_inline_max`` value (default
+ or specified explicitly in devargs) to reserve the space for inline data.
If ``txq_inline_min`` key is not present, the value may be queried by the
driver from the NIC via DevX if this feature is available. If there is no DevX
enabled/supported the value 18 (supposing L2 header including VLAN) is set
- for ConnectX-4, value 58 (supposing L2-L4 headers, required by configurations
- over E-Switch) is set for ConnectX-4 Lx, and 0 is set by default for ConnectX-5
+ for ConnectX-4 and ConnectX-4LX, and 0 is set by default for ConnectX-5
and newer NICs. If packet is shorter the ``txq_inline_min`` value, the entire
packet is inlined.
- For the ConnectX-4 and ConnectX-4 Lx NICs driver does not allow to set
- this value below 18 (minimal L2 header, including VLAN).
+ For ConnectX-4 NIC, driver does not allow specifying value below 18
+ (minimal L2 header, including VLAN), error will be raised.
+ For ConnectX-4LX NIC, it is allowed to specify values below 18, but
+ it is not recommended and may prevent NIC from sending packets over
+ some configurations.
Please, note, this minimal data inlining disengages eMPW feature (Enhanced
Multi-Packet Write), because last one does not support partial packet inlining.
More information about the dev