netdev - Re: [RFC PATCH net-next] veth: apply qdisc backpressure on full ptr

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Message-ID: <c908ce17-b2e9-472e-935c-f5133ddb9007@kernel.org>
Date: Mon, 7 Apr 2025 17:02:22 -0600
From: David Ahern <dsahern@...nel.org>
To: Toke Høiland-Jørgensen <toke@...hat.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>, netdev@...r.kernel.org,
 Jakub Kicinski <kuba@...nel.org>
Cc: bpf@...r.kernel.org, tom@...bertland.com,
 Eric Dumazet <eric.dumazet@...il.com>, "David S. Miller"
 <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>,
 kernel-team@...udflare.com
Subject: Re: [RFC PATCH net-next] veth: apply qdisc backpressure on full
 ptr_ring to reduce TX drops

On 4/7/25 3:15 AM, Toke Høiland-Jørgensen wrote:
>> +static inline bool txq_has_qdisc(struct netdev_queue *txq)
>> +{
>> +	struct Qdisc *q;
>> +
>> +	q = rcu_dereference(txq->qdisc);
>> +	if (q->enqueue)
>> +		return true;
>> +	else
>> +		return false;
>> +}
> 
> This seems like a pretty ugly layering violation, inspecting the qdisc
> like this in the driver?

vrf driver has something very similar - been there since March 2017.