netdev - Re: [PATCH v4 net-next 3/4] mlx4: xdp: Reserve headroom for receiving packet when XDP prog is active

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Message-ID: <CALzJLG9nKYhL=1G3g7UHvTruVn96O15WihySx41VEw7E_Xgq5w@mail.gmail.com>
Date:   Thu, 8 Dec 2016 20:47:30 +0200
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Martin KaFai Lau <kafai@...com>
Cc:     Linux Netdev List <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kubakici@...pl>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v4 net-next 3/4] mlx4: xdp: Reserve headroom for receiving
 packet when XDP prog is active

On Thu, Dec 8, 2016 at 1:53 AM, Martin KaFai Lau <kafai@...com> wrote:
> Reserve XDP_PACKET_HEADROOM for packet and enable bpf_xdp_adjust_head()
> support.  This patch only affects the code path when XDP is active.
>
> After testing, the tx_dropped counter is incremented if the xdp_prog sends
> more than wire MTU.
>

I guess this is the HW tx_dropped counter.  I suggest as a future
improvement to
drop in SW to save CPU and HW cycles on such packets.
Also those packets pages will be recycled immediately if dropped in
SW, one more extra point.

> Signed-off-by: Martin KaFai Lau <kafai@...com>

Acked-by: Saeed Mahameed <saeedm@...lanox.com>