netdev - Re: [PATCH RFC v3 0/5] Support fraglist GRO/GSO

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Message-ID: <20190919110125.GN2879@gauss3.secunet.de>
Date:   Thu, 19 Sep 2019 13:01:25 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
CC:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Network Development <netdev@...r.kernel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH RFC v3 0/5] Support fraglist GRO/GSO

On Wed, Sep 18, 2019 at 01:58:17PM -0300, Marcelo Ricardo Leitner wrote:
> On Wed, Sep 18, 2019 at 12:17:08PM -0400, Willem de Bruijn wrote:
> > 
> > More specifically, whether we can remove that in favor of using your
> > new skb_segment_list. That would actually be a big first step in
> > simplifying skb_segment back to something manageable.
> 
> The main issue (that I know) on obsoleting GSO_BY_FRAGS is that
> dealing with frags instead of frag_list was considered easier to be
> offloaded, if ever attempted.  So this would be a step back on that
> aspect.  Other than this, it should be doable.

I wonder why offloading the frag_list should be harder.
I looked at the i40e driver, it just iterates over the page
fragments found in skb_shinfo(skb)->frags in i40e_tx_map().

If the packet data of all the fraglist GRO skbs are backed by a
page fragment then we could just do the same by iterating with
skb_walk_frags(). I'm not a driver expert and might be misstaken,
but it looks like that could be done with existing hardware that
supports segmentation offload.