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

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Message-ID: <6e645155-1d2d-4b64-a19a-a6e90a12b684@redhat.com>
Date: Tue, 26 Aug 2025 08:33:50 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Eric Dumazet <edumazet@...gle.com>, "David S . Miller"
 <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>
Cc: 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 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?

Plus an additional conditional/casting in sk_drops_{read,inc,reset}.

That would save some memory also offer the opportunity to use more
memory to deal with  NUMA hosts.

(I had the crazy idea to keep sk_drop on a contended cacheline and use 2
(or more) cacheline aligned fields for udp_sock only).

Thanks,

Paolo