netdev - Re: [PATCH 01/12 v2 RFC] net: group skb_shinfo zerocopy related bits together.

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Message-ID: <CAF=yD-+i9o0_+2emOVkBw2JS5JyD+17zw-tJFdHiRyfHOz5LPQ@mail.gmail.com>
Date:   Tue, 22 Dec 2020 09:43:15 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Jonathan Lemon <jonathan.lemon@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH 01/12 v2 RFC] net: group skb_shinfo zerocopy related bits together.

On Mon, Dec 21, 2020 at 7:09 PM Jonathan Lemon <jonathan.lemon@...il.com> wrote:
>
> From: Jonathan Lemon <bsd@...com>
>
> In preparation for expanded zerocopy (TX and RX), move
> the ZC related bits out of tx_flags into their own flag
> word.
>
> Signed-off-by: Jonathan Lemon <jonathan.lemon@...il.com>

I think it's better to expand tx_flags to a u16 and add the two new
flags that you need.

That allows the additional 7 bits to be used for arbitrary flags, not
stranding 8 bits exactly only for zerocopy features.

Moving around a few u8's in the same cacheline won't be a problem.

I also prefer not to rename flags that some of us are familiar with,
if it's not needed.