Re: Enabling Byte Queue Limits in the ath5k wireless driver

[Simon Barber <simon@superduper.net>]

BQL or TQL are open-loop - there is no feedback. The amount of bytes or 
total packet transmission time in the queue is counted when packets 
enter and leave the queue, and a hard limit of total bytes or total time 
in queue is set. When I say time - I mean that on a packet entering the 
queue the total time the packet will take to transmit is calculated, and 
that time is added to a count to the total time currently in queue. When 
a packet has been transmitted the time is subtracted from the total time 
in queue. There would be no interference with CODEL running in front of 
this.

Simon

On 10/6/2013 6:31 AM, Anirudh Sivaraman wrote:
> On Sat, Oct 5, 2013 at 11:39 PM, Simon Barber <simon@superduper.net> wrote:
>> BQL does make sense, but TQL would be even better - 'Time Queue Limits'.
>> Which would work based on an estimate of how much time each packet will take
>> to send, and limiting the hardware queue to contain a total mount of 'time'.
>> The purpose of the hardware queue is to mask interrupt and other latencies
>> involved in refilling an empty queue - a time based phenomenon. Hence time
>> is the best metric to control it - with fixed speed interfaced like ethernet
>> bytes=time, but not so on wireless.
>>
> Thank you for your reply. TQL does make more sense for wireless at
> least. However, assuming that someone implement a qdisc like CoDel and
> attaches it to the wireless interface, doesn't TQL (or for that matter
> BQL) lead to two possibly competing control loops (one at the qdisc,
> and one at the device driver)?
>
> Anirudh
>> Simon
>>
>>
>> On 10/3/2013 11:49 AM, Anirudh Sivaraman wrote:
>>> Hi,
>>>
>>> I am looking into enabling BQL for the ath5k driver, and was wondering
>>> if anyone here knows of any prior efforts in this direction. In
>>> particular, is BQL even a sensible strategy for wireless drivers?
>>> Thank you in advance for any advice you may have in this regard.
>>>
>>> Anirudh
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>>
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