netdev - Re: EIO on send with UDP

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Message-ID: <87fs1gkthv.fsf@cloudflare.com>
Date: Wed, 08 Nov 2023 18:55:49 +0100
From: Jakub Sitnicki <jakub@...udflare.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org,
 kernel-team@...udflare.com
Subject: Re: EIO on send with UDP_SEGMENT

On Wed, Nov 08, 2023 at 10:10 AM -05, Willem de Bruijn wrote:
> On Wed, Nov 8, 2023 at 6:03 AM Jakub Sitnicki <jakub@...udflare.com> wrote:

[...]

>> Do you think the restriction in udp_send_skb can be lifted or tweaked?
>
> The argument against has been that segmentation offload offers no
> performance benefit if the stack has to fall back onto software
> checksumming.

Interesting. Thanks for sharing the context. Must admit, it would have
not been my first guess that the software GSO+checksum itself is not
worth it. Despite it happening late on the TX path.

> If this limitation makes userspace code more complex, by having to
> branch between segmentation offload and not depending on device
> features, that would be an argument to drop it. As you point out, it
> is not needed for correctness.

That answers my question. Thanks for feedback.