netdev - Re: [PATCH v2 net-next 0/6] net: optimize TX throughput and efficiency

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Message-ID: <CAM0EoMnvMZQpjNP5vCneur8GR+3oW3PxvzjtthNjFTtLBF5GtA@mail.gmail.com>
Date: Wed, 15 Oct 2025 18:00:20 -0400
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com
Subject: Re: [PATCH v2 net-next 0/6] net: optimize TX throughput and efficiency

On Tue, Oct 14, 2025 at 1:19 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> In this series, I replace the busylock spinlock we have in
> __dev_queue_xmit() and use lockless list (llist) to reduce
> spinlock contention to the minimum.
>
> Idea is that only one cpu might spin on the qdisc spinlock,
> while others simply add their skb in the llist.
>
> After this series, we get a 300 % (4x) improvement on heavy TX workloads,
> sending twice the number of packets per second, for half the cpu cycles.
>

Not important but i am curious: you didnt mention what NIC this was in
the commit messages ;->

For the patchset, I have done testing with existing tdc tests and no
regression..
It does inspire new things when time becomes available.... so will be
doing more testing and likely small extensions etc.
So:
Tested-by: Jamal Hadi Salim <jhs@...atatu.com>
Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
(For the tc bits, since the majority of the code touches tc related stuff)

cheers,
jamal


> v2: deflake tcp_user_timeout_user-timeout-probe.pkt.
>     Ability to return a different code than NET_XMIT_SUCCESS
>     when __dev_xmit_skb() has a single skb to send.
>
> Eric Dumazet (6):
>   selftests/net: packetdrill: unflake
>     tcp_user_timeout_user-timeout-probe.pkt
>   net: add add indirect call wrapper in skb_release_head_state()
>   net/sched: act_mirred: add loop detection
>   Revert "net/sched: Fix mirred deadlock on device recursion"
>   net: sched: claim one cache line in Qdisc
>   net: dev_queue_xmit() llist adoption
>
>  include/linux/netdevice_xmit.h                |  9 +-
>  include/net/sch_generic.h                     | 23 ++---
>  net/core/dev.c                                | 97 +++++++++++--------
>  net/core/skbuff.c                             | 11 ++-
>  net/sched/act_mirred.c                        | 62 +++++-------
>  net/sched/sch_generic.c                       |  7 --
>  .../tcp_user_timeout_user-timeout-probe.pkt   |  6 +-
>  7 files changed, 111 insertions(+), 104 deletions(-)
>
> --
> 2.51.0.788.g6d19910ace-goog
>