netdev - Re: [PATCH net] net_sched: limit try_bulk_dequeue

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Message-ID: <CANn89iJHVEbq_Cz8C6TGqOUig9xvC=joOeh_Anb+4uTW=Nyx6w@mail.gmail.com>
Date: Wed, 12 Nov 2025 03:21:58 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: Jamal Hadi Salim <jhs@...atatu.com>
Cc: kuba@...nel.org, davem@...emloft.net, pabeni@...hat.com, horms@...nel.org, 
	xiyou.wangcong@...il.com, jiri@...nulli.us, kuniyu@...gle.com, 
	willemb@...gle.com, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	hawk@...nel.org, patchwork-bot+netdevbpf@...nel.org, toke@...hat.com
Subject: Re: [PATCH net] net_sched: limit try_bulk_dequeue_skb() batches

On Wed, Nov 12, 2025 at 2:48 AM Jamal Hadi Salim <jhs@...atatu.com> wrote:
>
> On Tue, Nov 11, 2025 at 9:10 PM <patchwork-bot+netdevbpf@...nel.org> wrote:
> >
> > Hello:
> >
> > This patch was applied to netdev/net.git (main)
> > by Jakub Kicinski <kuba@...nel.org>:
> >
> > On Sun,  9 Nov 2025 16:12:15 +0000 you wrote:
> > > After commit 100dfa74cad9 ("inet: dev_queue_xmit() llist adoption")
> > > I started seeing many qdisc requeues on IDPF under high TX workload.
> > >
> > > $ tc -s qd sh dev eth1 handle 1: ; sleep 1; tc -s qd sh dev eth1 handle 1:
> > > qdisc mq 1: root
> > >  Sent 43534617319319 bytes 268186451819 pkt (dropped 0, overlimits 0 requeues 3532840114)
> > >  backlog 1056Kb 6675p requeues 3532840114
> > > qdisc mq 1: root
> > >  Sent 43554665866695 bytes 268309964788 pkt (dropped 0, overlimits 0 requeues 3537737653)
> > >  backlog 781164b 4822p requeues 3537737653
> > >
>
> Hrm. Should this have gone into net-next instead of net? Given that
> the changes causing regression are still in net-next.
> Dont think its a big deal if the merge is about to happen and i can
> manually apply it since i was going to run some tests today.
>
> cheers,
> jamal
>

Let me clarify : Before my recent work, I also had requeues but did
not care much.

Since then, I am trying to reduce the cost of TX, and latencies.

This try_bulk_dequeue_skb() was a major issue, I guess nobody caught it before.