netdev - Re: [PATCH net-next 2/4] mlx4: xdp: Allow raising MTU up to one page minus eth and vlan hdrs

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Date:   Fri, 02 Dec 2016 16:38:00 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     netdev@...r.kernel.org, Alexei Starovoitov <ast@...com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH net-next 2/4] mlx4: xdp: Allow raising MTU up to one
 page minus eth and vlan hdrs

On Fri, 2016-12-02 at 15:23 -0800, Martin KaFai Lau wrote:
> When XDP prog is attached, it is currently limiting
> MTU to be FRAG_SZ0 - ETH_HLEN - (2 * VLAN_HLEN) which is 1514
> in x86.
> 
> AFAICT, since mlx4 is doing one page per packet for XDP,
> we can at least raise the MTU limitation up to
> PAGE_SIZE - ETH_HLEN - (2 * VLAN_HLEN) which this patch is
> doing.  It will be useful in the next patch which allows
> XDP program to extend the packet by adding new header(s).
> 
> Signed-off-by: Martin KaFai Lau <kafai@...com>
> ---

Have you tested your patch on a host with PAGE_SIZE = 64 KB ?

Looks XDP really kills arches with bigger pages :(

Thanks.