From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Herbert Xu <herbert@gondor.apana.org.au>
Cc:     Johannes Berg <johannes@sipsolutions.net>,
        Arend Van Spriel <arend.vanspriel@broadcom.com>,
        Felix Fietkau <nbd@nbd.name>, linux-wireless@vger.kernel.org,
        Eric Dumazet <eric.dumazet@gmail.com>, netdev@vger.kernel.org
Subject: Re: [PATCH 5/5] mac80211: set NETIF_F_LLTX when using intermediate tx queues
In-Reply-To: <20190417033834.ep6t7r6ttvjek5g7@gondor.apana.org.au>
References: <20190416074444.pdubbh6fbibdnhi7@gondor.apana.org.au> <73b18131-2777-da5c-a6ee-9d9b3e13cd06@broadcom.com> <20190416083636.5ttvezqyhzr2worg@gondor.apana.org.au> <eab39dd804405854997e50102f3d0ff925feb8d2.camel@sipsolutions.net> <87ef62uwfm.fsf@toke.dk> <95f86cf69dee05a176625925657cf0df0e97b5c9.camel@sipsolutions.net> <20190416093707.dtlwcmitzqopaeaw@gondor.apana.org.au> <e4c1a3ca0c0c160b7c271ab83deebcf096f38497.camel@sipsolutions.net> <20190416131346.u2uolljlrd5t2jro@gondor.apana.org.au> <87wojut7f7.fsf@toke.dk> <20190417033834.ep6t7r6ttvjek5g7@gondor.apana.org.au>
Date:   Wed, 17 Apr 2019 10:09:16 +0100
Message-ID: <87wojtroar.fsf@toke.dk>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8BIT
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

Herbert Xu <herbert@gondor.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@gmail.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