Re: [PATCH V3 3/4] mac80211: fix low throughput in multi-clients situation

[Yibo Zhao <yiboz@codeaurora.org>]

On 2019-09-24 16:48, Toke Høiland-Jørgensen wrote:
> Yibo Zhao <yiboz@codeaurora.org> writes:
> 
>>> I can see why we need the second part (basically, this happens 
>>> because
>>> I
>>> forgot to add a check for "no eligible stations" in may_transmit(),
>>> like
>>> the one in next_txq()). And rounding up the division result doesn't
>>> hurt, I guess. But why does it help to change the grace period if 
>>> we're
>>> doing all the other stuff?
>> In multi-clients case, it is possible a TXQ sometimes gets drained due
>> to FW has deep queue and few packets in TXQ at that time. So the TXQ 
>> is
>> removed from the rbtree after dequeuing. When it is about to added 
>> back
>> very soon after the removal, the g_vt might have gone a little far 
>> away
>> from sta vt where sync is needed. With this sync, the station is 
>> forced
>> to catch up with the g_vt, however, its chance for transmission has 
>> been
>> reduced. I think 500us is quite a short period in multi-clients case.
> 
> That's a good point, actually: Having the grace period be too small 
> will
> allow stations that leave and re-enter the queue to "skip ahead" and 
> use
> more than its share. However, I think it's a separate issue from what
> this patch is about; so how about I just increase the grace period in
> the next version of the base patch?

Sure, no problem. :)
> 
> -Toke

-- 
Yibo