netdev - Re: [PATCH v15 01/20] net: Introduce direct data placement tcp offload

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Date: Thu, 21 Sep 2023 06:33:10 -0600
From: David Ahern <dsahern@...nel.org>
To: Aurelien Aptel <aaptel@...dia.com>, linux-nvme@...ts.infradead.org,
 netdev@...r.kernel.org, sagi@...mberg.me, hch@....de, kbusch@...nel.org,
 axboe@...com, chaitanyak@...dia.com, davem@...emloft.net, kuba@...nel.org
Cc: Boris Pismenny <borisp@...dia.com>, aurelien.aptel@...il.com,
 smalin@...dia.com, malin1024@...il.com, ogerlitz@...dia.com,
 yorayz@...dia.com, galshalom@...dia.com, mgurtovoy@...dia.com,
 edumazet@...gle.com, pabeni@...hat.com, imagedong@...cent.com
Subject: Re: [PATCH v15 01/20] net: Introduce direct data placement tcp
 offload

On 9/21/23 1:43 AM, Aurelien Aptel wrote:
> David Ahern <dsahern@...nel.org> writes:
>> Not consolidating frags into linear is a requirement for any Rx ZC
>> solution (e.g., the gpu devmem RFC set and accompanying io_uring set for
>> userspace memory). Meaning, the bit can be more generic and less tied to
>> ulp_ddp.
> 
> In our view the ULP Direct Data Placement has a very specific design and
> avoiding skb coalescing is just one aspect of it.
> It would be hard to make it generic for any type of zero copy design. We
> can rename the bit to "ddp" or "zerocopy" if you prefer but it might end
> up being more misleading.

The number of single use case bits on sk_buff are piling up. In this
case, skb->ulp_ddp is only used to avoid skb_condense, so name it
accordingly. skb->no_condense for example.