netdev - Re: [Patch net v6 4/8] net_sched: Implement the right netem duplication behavior

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Message-ID: <20260107181833.692a9ea1@kernel.org>
Date: Wed, 7 Jan 2026 18:18:33 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Cong Wang <xiyou.wangcong@...il.com>
Cc: Stephen Hemminger <stephen@...workplumber.org>, netdev@...r.kernel.org,
 William Liu <will@...lsroot.io>, Savino Dicanosa <savy@...t3mfailure.io>
Subject: Re: [Patch net v6 4/8] net_sched: Implement the right netem
 duplication behavior

On Wed, 7 Jan 2026 15:33:53 -0800 Cong Wang wrote:
> > It is worth testing for the case where netem is used as a leaf qdisc.
> > I worry that this could cause the parent qdisc to get accounting wrong.
> > I.e if HTB calls netem and netem queues 2 packets, the qlen in HTB
> > would be incorrect.  
> 
> In patch 6/8, I added "Test PRIO with NETEM duplication", which installs
> netem Qdisc as a child and leaf of root prio qdisc.
> 
> Or am I misunderstanding it?

Does something automatically validates that backlog is 0 when qdisc is
destroyed? The test itself only checks:

  "matchPattern": "Sent \\d+ bytes (\\d+) pkt",