netdev - Re: iwlwifi warnings in 5.5-rc1

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Message-ID: <87r21bez5g.fsf@toke.dk>
Date:   Wed, 11 Dec 2019 15:04:59 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Johannes Berg <johannes@...solutions.net>,
        Jens Axboe <axboe@...nel.dk>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>
Cc:     "linux-wireless\@vger.kernel.org" <linux-wireless@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: iwlwifi warnings in 5.5-rc1

Johannes Berg <johannes@...solutions.net> writes:

> Btw, there's *another* issue. You said in the commit log:
>
>     This patch does *not* include any mechanism to wake a throttled TXQ again,
>     on the assumption that this will happen anyway as a side effect of whatever
>     freed the skb (most commonly a TX completion).
>
> Thinking about this some more, I'm not convinced that this assumption
> holds. You could have been stopped due to the global limit, and now you
> wake some queue but the TXQ is empty - now you should reschedule some
> *other* TXQ since the global limit had kicked in, not the per-TXQ limit,
> and prevented dequeuing, no?

Well if you hit the global limit that means you have 24ms worth of data
queued in the hardware; those should be completed in turn, and enable
more to be dequeued, no?

-Toke