From: Jakub Kicinski <kuba@kernel.org>
To: Eric Dumazet <edumazet@google.com>
Cc: "David S . Miller" <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
Willem de Bruijn <willemb@google.com>,
Kuniyuki Iwashima <kuniyu@google.com>,
netdev@vger.kernel.org, eric.dumazet@gmail.com
Subject: Re: [PATCH v2 net-next] udp: remove busylock and add per NUMA queues
Date: Sat, 20 Sep 2025 11:10:59 -0700 [thread overview]
Message-ID: <20250920111059.500c2b8f@kernel.org> (raw)
In-Reply-To: <20250920080227.3674860-1-edumazet@google.com>
On Sat, 20 Sep 2025 08:02:27 +0000 Eric Dumazet wrote:
> busylock was protecting UDP sockets against packet floods,
> but unfortunately was not protecting the host itself.
>
> Under stress, many cpus could spin while acquiring the busylock,
> and NIC had to drop packets. Or packets would be dropped
> in cpu backlog if RPS/RFS were in place.
>
> This patch replaces the busylock by intermediate
> lockless queues. (One queue per NUMA node).
>
> This means that fewer number of cpus have to acquire
> the UDP receive queue lock.
>
> Most of the cpus can either:
> - immediately drop the packet.
> - or queue it in their NUMA aware lockless queue.
>
> Then one of the cpu is chosen to process this lockless queue
> in a batch.
>
> The batch only contains packets that were cooked on the same
> NUMA node, thus with very limited latency impact.
Occasionally hitting a UaF like this:
https://netdev-3.bots.linux.dev/vmksft-net-dbg/results/306342/3-fcnal-ipv6-sh/stderr
decoded:
https://netdev-3.bots.linux.dev/vmksft-net-dbg/results/306342/vm-crash-thr2-0
--
pw-bot: cr
next prev parent reply other threads:[~2025-09-20 18:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-20 8:02 [PATCH v2 net-next] udp: remove busylock and add per NUMA queues Eric Dumazet
2025-09-20 18:10 ` Jakub Kicinski [this message]
2025-09-20 19:38 ` Eric Dumazet
2025-09-20 18:33 ` [syzbot ci] " syzbot ci
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