netdev - Re: [PATCH net-next 3/3] net: add new sk->sk

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Message-ID: <CANn89iLaYB_zS2u4jdrfSkqa=V-fHQnttxSZR2B6-5oK6RU+uQ@mail.gmail.com>
Date: Tue, 26 Aug 2025 05:11:39 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Willem de Bruijn <willemb@...gle.com>, Kuniyuki Iwashima <kuniyu@...gle.com>
Subject: Re: [PATCH net-next 3/3] net: add new sk->sk_drops1 field

On Tue, Aug 26, 2025 at 12:16 AM Paolo Abeni <pabeni@...hat.com> wrote:
>
> On 8/26/25 8:46 AM, Eric Dumazet wrote:
> > On Mon, Aug 25, 2025 at 11:34 PM Paolo Abeni <pabeni@...hat.com> wrote:
> >> On 8/25/25 9:59 PM, Eric Dumazet wrote:
> >>> sk->sk_drops can be heavily contended when
> >>> changed from many cpus.
> >>>
> >>> Instead using too expensive per-cpu data structure,
> >>> add a second sk->sk_drops1 field and change
> >>> sk_drops_inc() to be NUMA aware.
> >>>
> >>> This patch adds 64 bytes per socket.
> >>
> >> I'm wondering: since the main target for dealing with drops are UDP
> >> sockets, have you considered adding sk_drops1 to udp_sock, instead?
> >
> > I actually saw the issues on RAW sockets, some applications were using them
> > in a non appropriate way. This was not an attack on single UDP sockets, but
> > a self-inflicted issue on RAW sockets.
> >
> > Author: Eric Dumazet <edumazet@...gle.com>
> > Date:   Thu Mar 7 16:29:43 2024 +0000
> >
> >     ipv6: raw: check sk->sk_rcvbuf earlier
> >
> >     There is no point cloning an skb and having to free the clone
> >     if the receive queue of the raw socket is full.
> >
> >     Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> >     Reviewed-by: Willem de Bruijn <willemb@...gle.com>
> >     Link: https://lore.kernel.org/r/20240307162943.2523817-1-edumazet@google.com
> >     Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>
> I see, thanks for the pointer. Perhaps something alike the following
> (completely untested) could fit? With similar delta for raw sock and
> sk_drops_{read,inc,reset} would check sk_drop_counters and ev. use it
> instead of sk->sk_drop. Otherwise I have no objections at all!

Good idea.

In v2, I will only add the extra space for UDP and RAW sockets.

Thanks !