netdev - Re: [PATCH net-next] net_sched: restore "mpu xxx" handling

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Date:   Tue, 11 Jan 2022 21:06:13 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Kevin Bracey <kevin@...cey.fi>
Cc:     <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>,
        Jiri Pirko <jiri@...nulli.us>, Vimalkumar <j.vimal@...il.com>
Subject: Re: [PATCH net-next] net_sched: restore "mpu xxx" handling

On Fri, 7 Jan 2022 22:22:50 +0200 Kevin Bracey wrote:
> commit 56b765b79e9a ("htb: improved accuracy at high rates") broke
> "overhead X", "linklayer atm" and "mpu X" attributes.
> 
> "overhead X" and "linklayer atm" have already been fixed. This restores
> the "mpu X" handling, as might be used by DOCSIS or Ethernet shaping:
> 
>     tc class add ... htb rate X overhead 4 mpu 64
> 
> The code being fixed is used by htb, tbf and act_police. Cake has its
> own mpu handling. qdisc_calculate_pkt_len still uses the size table
> containing values adjusted for mpu by user space.
> 
> Fixes: 56b765b79e9a ("htb: improved accuracy at high rates")

Are you sure this worked and got broken? I can't seem to grep out any
uses of mpu in this code. commit 175f9c1bba9b ("net_sched: Add size
table for qdiscs") adds it as part of the struct but I can't find a
single use of it.