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Re: [PATCH] ath10k: remove iteration in wake_tx_queue

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Erik Stromdahl <erik.stromdahl@xxxxxxxxx> writes:

> On 4/16/19 9:07 PM, Toke Høiland-Jørgensen wrote:
>> Erik Stromdahl <erik.stromdahl@xxxxxxxxx> writes:
>>
>>> On 4/1/19 1:05 PM, Toke Høiland-Jørgensen wrote:
>>>> Erik Stromdahl <erik.stromdahl@xxxxxxxxx> 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).

It will take a while before these commits trickle down to ath-next
branch, most likely after v5.2-rc1 is released.

-- 
Kalle Valo




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