netdev - Re: [PATCH 5/5] mac80211: set NETIF_F_LLTX when using intermediate tx queues

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Date:   Wed, 17 Apr 2019 10:09:16 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Johannes Berg <johannes@...solutions.net>,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        Felix Fietkau <nbd@....name>, linux-wireless@...r.kernel.org,
        Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH 5/5] mac80211: set NETIF_F_LLTX when using intermediate tx queues

Herbert Xu <herbert@...dor.apana.org.au> writes:

> On Tue, Apr 16, 2019 at 02:18:36PM +0100, Toke Høiland-Jørgensen wrote:
>>
>> > The congestion control happens at two levels. You are right that the
>> > socket buffer acts as one limit. However, other applications may also
>> > rely on the TX queue being full as the throttle (by setting a
>> > sufficiently large socket buffer size).
>> 
>> Do you happen to have an example of an application that does this that
>> could be used for testing? :)
>
> Have a look at
>
> commit 6ce9e7b5fe3195d1ae6e3a0753d4ddcac5cd699e
> Author: Eric Dumazet <eric.dumazet@...il.com>
> Date:   Wed Sep 2 18:05:33 2009 -0700
>
>     ip: Report qdisc packet drops
>
> You should be able to do a UDP flood while setting IP_RECVERR to
> detect the packet drop due to a full queue which AFAICS will never
> happen with the current mac80211 setup.

Yup, got that part. Was just wondering if you know of any applications
that already do this, that I could test without having to write my
own... :)

-Toke