Re: [Make-wifi-fast] [v6] ath9k: Switch to using mac80211 intermediate software queues.

["Toke Høiland-Jørgensen" <toke@toke.dk>]

Kalle Valo <kvalo@qca.qualcomm.com> writes:

> Toke Høiland-Jørgensen wrote:
>> This switches ath9k over to using the mac80211 intermediate software
>> queueing mechanism for data packets. It removes the queueing inside the
>> driver, except for the retry queue, and instead pulls from mac80211 when
>> a packet is needed. The retry queue is used to store a packet that was
>> pulled but can't be sent immediately.
>> 
>> The old code path in ath_tx_start that would queue packets has been
>> removed completely, as has the qlen limit tunables (since there's no
>> longer a queue in the driver to limit).
>> 
>> The mac80211 intermediate software queues offer significant latency
>> reductions, and this patch allows ath9k to realise them. The exact gains
>> from this varies with the test scenario, but in an access point scenario
>> we have seen latency reductions ranging from 1/3 to as much as an order
>> of magnitude. We also achieve slightly better aggregation.
>> 
>> Median latency (ping) figures with this patch applied at the access point,
>> with two high-rate stations and one low-rate station (HT20 5Ghz), running
>> a Flent rtt_fair_var_up test with one TCP flow and one ping flow going to
>> each station:
>> 
>>                                  Fast station        Slow station
>> Default pfifo_fast qdisc:            430.4 ms            638.7 ms
>> fq_codel qdisc on iface:              35.5 ms            211.8 ms
>> This patch set:                       22.4 ms             38.2 ms
>> 
>> Median aggregation sizes over the same test:
>> 
>> Default pfifo_fast qdisc:            9.5 pkts            1.9 pkts
>> fq_codel qdisc on iface:            11.2 pkts            1.9 pkts
>> This patch set:                     13.9 pkts            1.9 pkts
>> 
>> This patch is based on Tim's original patch set, but reworked quite
>> thoroughly.
>> 
>> Cc: Tim Shepard <shep@alum.mit.edu>
>> Cc: Felix Fietkau <nbd@nbd.name>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
>
> Perfect, just what I was hoping to see :) Unless something really
> surprising comes up I should apply this within the next few days.

Awesome, thanks! :)

-Toke