netdev - RE: [PATCH net-next v2 12/33] hv_netvsc: add XDP frame size to driver

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Message-ID: <MN2PR21MB1437A4F44AC313E5DF962B35CAAA0@MN2PR21MB1437.namprd21.prod.outlook.com>
Date:   Thu, 30 Apr 2020 14:20:20 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>,
        "sameehj@...zon.com" <sameehj@...zon.com>
CC:     Wei Liu <wei.liu@...nel.org>, KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "zorik@...zon.com" <zorik@...zon.com>,
        "akiyano@...zon.com" <akiyano@...zon.com>,
        "gtzalik@...zon.com" <gtzalik@...zon.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        David Ahern <dsahern@...il.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "steffen.klassert@...unet.com" <steffen.klassert@...unet.com>
Subject: RE: [PATCH net-next v2 12/33] hv_netvsc: add XDP frame size to driver



> -----Original Message-----
> From: Jesper Dangaard Brouer <brouer@...hat.com>
> Sent: Thursday, April 30, 2020 7:21 AM
> To: sameehj@...zon.com
> Cc: Wei Liu <wei.liu@...nel.org>; KY Srinivasan <kys@...rosoft.com>;
> Haiyang Zhang <haiyangz@...rosoft.com>; Stephen Hemminger
> <sthemmin@...rosoft.com>; Jesper Dangaard Brouer
> <brouer@...hat.com>; netdev@...r.kernel.org; bpf@...r.kernel.org;
> zorik@...zon.com; akiyano@...zon.com; gtzalik@...zon.com; Toke
> Høiland-Jørgensen <toke@...hat.com>; Daniel Borkmann
> <borkmann@...earbox.net>; Alexei Starovoitov
> <alexei.starovoitov@...il.com>; John Fastabend
> <john.fastabend@...il.com>; Alexander Duyck
> <alexander.duyck@...il.com>; Jeff Kirsher <jeffrey.t.kirsher@...el.com>;
> David Ahern <dsahern@...il.com>; Willem de Bruijn
> <willemdebruijn.kernel@...il.com>; Ilias Apalodimas
> <ilias.apalodimas@...aro.org>; Lorenzo Bianconi <lorenzo@...nel.org>;
> Saeed Mahameed <saeedm@...lanox.com>;
> steffen.klassert@...unet.com
> Subject: [PATCH net-next v2 12/33] hv_netvsc: add XDP frame size to driver
> 
> The hyperv NIC drivers XDP implementation is rather disappointing as it will
> be a slowdown to enable XDP on this driver, given it will allocate a new page
> for each packet and copy over the payload, before invoking the XDP BPF-
> prog.
This needs correction. As I said previously -- 
This statement is not accurate -- The data path of netvsc driver does memory 
allocation and copy even without XDP, so it's not "a slowdown to enable XDP".

Thanks,
- Haiyang