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    Subject[PATCH 4.9 29/54] net/mlx5e: Fix small packet threshold
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eugenia Emantayev <eugenia@mellanox.com>


    [ 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@mellanox.com>
    Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    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) <= U16_MAX)

    #define MLX5_UMR_ALIGN (2048)
    -#define MLX5_MPWRQ_SMALL_PACKET_THRESHOLD (128)
    +#define MLX5_MPWRQ_SMALL_PACKET_THRESHOLD (256)

    #define MLX5E_PARAMS_DEFAULT_LRO_WQE_SZ (64 * 1024)
    #define MLX5E_DEFAULT_LRO_TIMEOUT 32

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