path: root/doc/guides/nics/mlx5.rst
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authorShahaf Shuler <>2017-09-14 13:50:39 +0300
committerFerruh Yigit <>2017-10-06 02:49:48 +0200
commit883ce1724b652d8da1cacdaf8409580b24d6a33d (patch)
tree931e290a7b2f9815bef0de65e8911d75f0727a2d /doc/guides/nics/mlx5.rst
parent24c14430cdc4556a30a1e608f67230e881718f7f (diff)
net/mlx5: enforce Tx num of segments limitation
Mellanox NICs has a limitation on the number of mbuf segments a multi segment mbuf can have. The max number depends on the Tx offloads requested. The current code not enforce such limitation, which might cause malformed work requests to be written to the device. This commit adds verification for the number of mbuf segments posted to the device. In case of overflow the packet will not be sent. In addition update the nic documentation with the limitation. Considering device limitation is 63 data segments in a work request, the maximum number of segment in mbuf was calculated taking TSO as the worst case: max_nb_segs = 63 - (control_segment + ethernet segment + TSO headers inline + inline segment + extra inline to align to cacheline) Cc: Signed-off-by: Shahaf Shuler <> Acked-by: Yongseok Koh <> Acked-by: Nelio Laranjeiro <>
Diffstat (limited to 'doc/guides/nics/mlx5.rst')
1 files changed, 4 insertions, 0 deletions
diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index f4cb18b..c6a196c 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -124,6 +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.