Linux ath11k Driver Improvements For Qualcomm WiFi 6 Hardware Yields 7x Lower Latency

A patch series being worked on for the ath11k mainline wireless networking driver for Qualcomm WiFi 6 / 802.11ax chipsets is yielding 7x lower latency or 2.2x throughput at identical latency.

Open-source developer Julius Bairaktaris has been addressing the ath11k driver's lack of a queue of its own that in turn is crippling the network latency with major inefficiencies. Bairaktaris explained with the patch series cover letter:

"ath11k advertises neither NL80211_EXT_FEATURE_AQL nor NL80211_EXT_FEATURE_AIRTIME_FAIRNESS, and every user of either inside mac80211 is gated on the corresponding bit. Both mechanisms are inert on this driver, and the driver keeps no queue of its own, so on a saturated download every queued byte sits in the hardware TX rings, where there is no AQM and no flow separation.

Measured on an IPQ8074 access point serving one HE station: saturated TCP downstream, a 20 Hz probe from that station through the same access category, arms interleaved, three pairs each.

stock 94.6 Mbit/s 155 ms
series, default limit 94.0 Mbit/s 157 ms
series, BE aql_txq_limit 500/1000 74.3 Mbit/s 22 ms
the same, patch 6 reverted 33.7 Mbit/s 21 ms

On stock, mac80211 reports no pending airtime and one frame of FQ-CoDel backlog, and aql_txq_limit has the same effect at either setting, which is none. The series puts the queue back under mac80211's control at no cost where the limit does not bind, and roughly seven times lower latency where it does. Patch 6, the completion-driven scheduling round, is worth 2.2x throughput at identical latency and nothing at the default limit."

Exciting work.

The nine patches adding just over 150 lines of code were assisted by Claude Opus 5. The code is under review on the Linux kernel mailing list.