From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: David Ahern <dsahern@kernel.org>,
Jesper Dangaard Brouer <hawk@kernel.org>,
netdev@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>
Cc: bpf@vger.kernel.org, tom@herbertland.com,
Eric Dumazet <eric.dumazet@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>,
kernel-team@cloudflare.com
Subject: Re: [RFC PATCH net-next] veth: apply qdisc backpressure on full ptr_ring to reduce TX drops
Date: Tue, 08 Apr 2025 13:23:14 +0200 [thread overview]
Message-ID: <87h62yx5gd.fsf@toke.dk> (raw)
In-Reply-To: <c908ce17-b2e9-472e-935c-f5133ddb9007@kernel.org>
David Ahern <dsahern@kernel.org> writes:
> 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.
Doesn't make it any less ugly, though ;)
And AFAICT, vrf is doing more with the information; basically picking a
whole different TX path? Can you elaborate on the reasoning for this (do
people actually install qdiscs on VRF devices in practice)?
-Toke
next prev parent reply other threads:[~2025-04-08 11:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-04 14:49 [RFC PATCH net-next] veth: apply qdisc backpressure on full ptr_ring to reduce TX drops Jesper Dangaard Brouer
2025-04-04 19:51 ` Jesper Dangaard Brouer
2025-04-07 9:15 ` Toke Høiland-Jørgensen
2025-04-07 12:42 ` Jesper Dangaard Brouer
2025-04-07 23:02 ` David Ahern
2025-04-08 11:23 ` Toke Høiland-Jørgensen [this message]
2025-04-08 15:20 ` David Ahern
2025-04-07 17:02 ` Simon Horman
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