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

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Message-ID: <20200501164703.75eb5737@carbon>
Date:   Fri, 1 May 2020 16:47:03 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     "sameehj@...zon.com" <sameehj@...zon.com>,
        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>,
        brouer@...hat.com
Subject: Re: [PATCH net-next v2 12/33] hv_netvsc: add XDP frame size to
 driver

On Thu, 30 Apr 2020 14:20:20 +0000
Haiyang Zhang <haiyangz@...rosoft.com> wrote:
> > -----Original Message-----
> > From: Jesper Dangaard Brouer <brouer@...hat.com>
> > 
> > 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".

Okay, I have changed the paragraph text to:

 The hyperv NIC driver does memory allocation and copy even without XDP.
 In XDP mode it will allocate a new page for each packet and copy over
 the payload, before invoking the XDP BPF-prog.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer