netdev - Re: [PATCH net-next 00/10] net_sched: speedup qdisc dequeue

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Message-ID: <20251110084432.7fdf647b@kernel.org>
Date: Mon, 10 Nov 2025 08:44:32 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Paolo Abeni
 <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Jamal Hadi Salim
 <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko
 <jiri@...nulli.us>, "Toke Høiland-Jørgensen"
 <toke@...hat.com>, Kuniyuki Iwashima <kuniyu@...gle.com>, Willem de Bruijn
 <willemb@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next 00/10] net_sched: speedup qdisc dequeue

On Mon, 10 Nov 2025 09:44:55 +0000 Eric Dumazet wrote:
> Avoid up to two cache line misses in qdisc dequeue() to fetch
> skb_shinfo(skb)->gso_segs/gso_size while qdisc spinlock is held.
> 
> Idea is to cache gso_segs at enqueue time before spinlock is
> acquired, in the first skb cache line, where we already
> have qdisc_skb_cb(skb)->pkt_len.
> 
> This series gives a 8 % improvement in a TX intensive workload.
> 
> (120 Mpps -> 130 Mpps on a Turin host, IDPF with 32 TX queues)

According to CI this breaks a bunch of tests.

https://netdev.bots.linux.dev/contest.html?branch=net-next-2025-11-10--12-00

I think they all hit:

[   20.682474][  T231] WARNING: CPU: 3 PID: 231 at ./include/net/sch_generic.h:843 __dev_xmit_skb+0x786/0x1550