netdev - RE: [PATCH intel-next 0/5] i40e: support XDP multi-buffer

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Date:   Wed, 14 Dec 2022 15:56:15 +0000
From:   "Sarkar, Tirthendu" <tirthendu.sarkar@...el.com>
To:     Alexander H Duyck <alexander.duyck@...il.com>,
        "tirtha@...il.com" <tirtha@...il.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "hawk@...nel.org" <hawk@...nel.org>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        "Fijalkowski, Maciej" <maciej.fijalkowski@...el.com>
Subject: RE: [PATCH intel-next 0/5] i40e: support XDP multi-buffer

> From: Alexander H Duyck <alexander.duyck@...il.com>
> Sent: Tuesday, December 13, 2022 9:28 PM
> 
> This approach seems kind of convoluted to me. Basically you are trying
> to clean the ring without cleaning the ring in the cases where you
> encounter a non EOP descriptor.
> 
> Why not just replace the skb pointer with an xdp_buff in the ring? Then
> you just build an xdp_buff w/ frags and then convert it after after
> i40e_is_non_eop? You should then still be able to use all the same page
> counting tricks and the pages would just be dropped into the shared
> info of an xdp_buff instead of an skb and function the same assuming
> you have all the logic in place to clean them up correctly.

We have another approach similar to what you have suggested which sort 
of is a bit cleaner but not free of a burden of getting the rx_buffer struct 
back again for all of the packet frags post i40e_run_xdp() for recycling.
We will examine if that turns out to be better.