On Wed, 2018-09-05 at 11:47 +0200, Toke Høiland-Jørgensen wrote: > Johannes Berg <johannes@xxxxxxxxxxxxxxxx> writes: > > > From: Johannes Berg <johannes.berg@xxxxxxxxx> > > > > Some frames may have a non-zero skb->priority assigned by > > mac80211 internally, e.g. TDLS setup frames, regardless of > > support for QoS. > > > > Currently, we set skb->priority to 0 for all data frames. > > Note that there's a comment that this is "required for > > correct WPA/11i MIC", but that doesn't seem true as we use > > > > if (ieee80211_is_data_qos(hdr->frame_control)) > > qos_tid = ieee80211_get_tid(hdr); > > else > > qos_tid = 0; > > > > in the code there. We could therefore reconsider this, but > > it seems like unnecessary complexity for the unlikely (and > > not very useful) case of not having QoS on the connection. > > > > This situation then causes something strange - most data > > frames will go on TXQ for TID 0 for non-QoS connections, > > but very few exceptions that are internally generated will > > go on another TXQ, possibly causing confusion. > > What kind of confusion are you seeing? Reordering issues, or something > else? I haven't actually been able to test this... But with the iwlwifi work we're doing, at the very least we'd waste a hardware queue for the case that basically never happens, since you'd end up putting these frames (that are very few) on a separate TXQ and thus hardware queue. You could argue we should explicitly _not_ do this, but then we should also set skb->priority to be non-zero for non-QoS stations. Then we could benefit from some form of QoS (between the TXQs) for non-QoS connections, but that seems pretty complex and doesn't seem worth it since all connections that want anything from HT/11n and newer need QoS anyway. So basically this gets rid of a corner case that we shouldn't have. Either we should decide that using different TXQs is *always* correct for non-QoS, or - what I thought - that this isn't worth it, and then we should *never* do it. johannes
