netdev - Re: [PATCH v3 net-next] udp: remove busylock and add per NUMA queues

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Message-ID: <4b38257b-c968-4128-bf4f-1a677da37972@redhat.com>
Date: Mon, 22 Sep 2025 11:27:58 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski
 <kuba@...nel.org>, Simon Horman <horms@...nel.org>,
 Willem de Bruijn <willemb@...gle.com>, Kuniyuki Iwashima
 <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH v3 net-next] udp: remove busylock and add per NUMA queues

On 9/22/25 10:47 AM, Eric Dumazet wrote:
> On Mon, Sep 22, 2025 at 1:37 AM Paolo Abeni <pabeni@...hat.com> wrote:
>> What if the user-space process never reads the packets (or is very
>> slow)? I'm under the impression the max rcvbuf occupation will be
>> limited only by the memory accounting?!? (and not by sk_rcvbuf)
> 
> Well, as soon as sk->sk_rmem_alloc is bigger than sk_rcvbuf, all
> further incoming packets are dropped.
> 
> As you said, memory accounting is there.
> 
> This could matter if we had thousands of UDP sockets under flood at
> the same time,
> but that would require thousands of cpus and/or NIC rx queues.

Ah, I initially misread:

	rmem += atomic_read(&udp_prod_queue->rmem_alloc);

as
	rmem = atomic_read(&udp_prod_queue->rmem_alloc);

and was fooled on the overall boundary check. LGTM now, thanks!

Paolo