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

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Message-ID: <20190417033834.ep6t7r6ttvjek5g7@gondor.apana.org.au>
Date:   Wed, 17 Apr 2019 11:38:34 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
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

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.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt