[PATCH 4.10 34/62] net/mlx5e: Fix small packet threshold

From: Greg Kroah-Hartman
Date: Mon May 01 2017 - 17:43:07 EST

4.10-stable review patch. If anyone has any objections, please let me know.


From: Eugenia Emantayev <eugenia@xxxxxxxxxxxx>

[ Upstream commit cbad8cddb6ed7ef3a5f0a9a70f1711d4d7fb9a8f ]

RX packet headers are meant to be contained in SKB linear part,
and chose a threshold of 128.
It turns out this is not enough, i.e. for IPv6 packet over VxLAN.
In this case, UDP/IPv4 needs 42 bytes, GENEVE header is 8 bytes,
and 86 bytes for TCP/IPv6. In total 136 bytes that is more than
current 128 bytes. In this case expand header flow is reached.
The warning in skb_try_coalesce() caused by a wrong truesize
was already fixed here:
commit 158f323b9868 ("net: adjust skb->truesize in pskb_expand_head()").
Still, we prefer to totally avoid the expand header flow for performance reasons.
Tested regular TCP_STREAM with iperf for 1 and 8 streams, no degradation was found.

Fixes: 461017cb006a ("net/mlx5e: Support RX multi-packet WQE (Striding RQ)")
Signed-off-by: Eugenia Emantayev <eugenia@xxxxxxxxxxxx>
Signed-off-by: Saeed Mahameed <saeedm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/net/ethernet/mellanox/mlx5/core/en.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -82,7 +82,7 @@
#define MLX5E_VALID_NUM_MTTS(num_mtts) (MLX5_MTT_OCTW(num_mtts) - 1 <= U16_MAX)

#define MLX5_UMR_ALIGN (2048)

#define MLX5E_PARAMS_DEFAULT_LRO_WQE_SZ (64 * 1024)