netdev - Re: [PATCH net-next] net: minor __alloc

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Message-ID: <20260113183008.15175891@kernel.org>
Date: Tue, 13 Jan 2026 18:30:08 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Paolo Abeni
 <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] net: minor __alloc_skb() optimization

On Wed, 14 Jan 2026 02:54:10 +0100 Eric Dumazet wrote:
> We could keep it for a while, WDYT of
> 
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 77508cf7c41e829a11a988d8de3d2673ff1ff121..ccd287ff46e91c2548483c51fa32fc6167867940
> 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -458,7 +458,8 @@ static void __build_skb_around(struct sk_buff
> *skb, void *data,
>         /* frag_size == 0 is considered deprecated now. Callers
>          * using slab buffer should use slab_build_skb() instead.
>          */
> -       if (WARN_ONCE(size == 0, "Use slab_build_skb() instead"))
> +       if (IS_ENABLED(CONFIG_DEBUG_NET) &&
> +           WARN_ONCE(size == 0, "Use slab_build_skb() instead"))
>                 data = __slab_build_skb(data, &size);

Probably not worth it. People who use relevant HW + 3 year old kernels
(I just checked, we added the warning in Dec 2022) likely don't set
DEBUG_NET either. That said looks like the warning landed in 6.2,
narrowly missing the v6.1 LTS. I suppose v6.1 may still be used by some
"enterprise-ish" distroes. I guess we should wait another year :(
Sorry for the noise :(