Subject: Re: [PATCH] ath10k: remove iteration in wake_tx_queue
To:     =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= <toke@redhat.com>,
        kvalo@qca.qualcomm.com, linux-wireless@vger.kernel.org,
        ath10k@lists.infradead.org
Cc:     yiboz@codeaurora.org
References: <20190327162906.6010-1-erik.stromdahl@gmail.com>
 <87bm1qq92j.fsf@toke.dk> <8772dfe6-3f52-05ca-f55a-b7eae14fa7ac@gmail.com>
 <87imvdu5u8.fsf@toke.dk>
From:   Erik Stromdahl <erik.stromdahl@gmail.com>
Message-ID: <f915fa20-a4e1-7312-dea2-d60b716e4877@gmail.com>
Date:   Wed, 17 Apr 2019 15:29:41 +0200
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On 4/16/19 9:07 PM, Toke Høiland-Jørgensen wrote:
> Erik Stromdahl <erik.stromdahl@gmail.com> writes:
> 
>> On 4/1/19 1:05 PM, Toke Høiland-Jørgensen wrote:
>>> Erik Stromdahl <erik.stromdahl@gmail.com> writes:
>>>
>>>> Iterating the TX queue and thereby dequeuing all available packets in the
>>>> queue could result in performance penalties on some SMP systems.
>>>>
>>>> The reason for this is most likely that the per-ac lock (active_txq_lock)
>>>> in mac80211 will be held by the CPU iterating the current queue.
>>>>
>>>> This will lock up other CPUs trying to push new messages on the TX
>>>> queue.
>>>>
>>>> Instead of iterating the queue we fetch just one packet at the time,
>>>> resulting in minimal starvation of the other CPUs.
>>>
>>> Did you test this with Felix' patches reducing the time the lock is held
>>> in mac80211?
>>>
>>> -Toke
>>>
>> Hi Toke,
>>
>> I am not aware of these patches. Can you please point them out for me?
> 
> They've already been merged. Commits dcec1d9bc8a7 and 7ef769459f14 in
> mac80211-next :)
> 
> -Toke
> 

I see. I am using the ath tree and I couldn't find them there.
I can cherry-pick them to my own tree and try them out
(or wait until Kalle updates ath.git).

--
Erik