Re: [PATCH v6 4/4] mac80211: Use Airtime-based Queue Limits (AQL) on packet dequeue

[Johannes Berg <johannes@sipsolutions.net>]

On Wed, 2019-10-23 at 11:59 +0200, Toke Høiland-Jørgensen wrote:
> 
> +	if (info->tx_time_est) {
> +		struct sta_info *sta = NULL, *s;
> +		struct rhlist_head *tmp;
> +
> +		rcu_read_lock();
> +
> +		for_each_sta_info(local, hdr->addr1, s, tmp) {
> +			/* skip wrong virtual interface */
> +			if (!ether_addr_equal(hdr->addr2, s->sdata->vif.addr))
> +				continue;
> +
> +			sta = s;
> +			break;
> +		}

I guess that is better than looking up the sdata and then using
sta_info_get(), but I think I'd like to see this wrapped into a function
(even if it's an inline) in sta_info.{c,h}.

> +		airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta,
> +							     skb->len);
> +		if (airtime) {
> +			/* We only have 10 bits in tx_time_est, so store airtime
> +			 * in increments of 4us and clamp the maximum to 2**12-1
> +			 */
> +			airtime = min_t(u32, airtime, 4095) & ~3U;
> +			info->tx_time_est = airtime >> 2;
> +			ieee80211_sta_update_pending_airtime(local, tx.sta,
> +							     txq->ac, airtime,
> +							     false);

I wonder if it'd be better to pass the shifted value to
ieee80211_sta_update_pending_airtime() to avoid all the shifting in all
places?

You could even store the shifted value in "aql_tx_pending" and
"aql_total_pending_airtime" etc., it's completely equivalent, and only
shift it out for people looking at debugfs.

johannes