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

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Message-ID: <CANn89iLqjm6UE+VkHW9P1X3nSpU9Aih+BYVrrfnQYnC-VHnUkw@mail.gmail.com>
Date: Mon, 22 Sep 2025 05:58:39 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, 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 Mon, Sep 22, 2025 at 5:38 AM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> Of course. Thanks. Nice lockless multi-producer multi-consumer struct.
> I had not seen it before. A try_cmpxchg and xchg pair, but on an
> uncontended NUMA local cacheline in the normal case.

I have played with a similar strategy for skb_attempt_defer_free(), I
am still polishing a series.

For some reason, spin_lock() on recent platforms is extremely expensive,
when false sharing is occurring.