On 25.05.22 14:14, Baligh GASMI wrote:
> Since the integration of AQL, packet TX airtime estimation is
> calculated and counted to be used for the dequeue limit.
>
> Use this estimated airtime to compute expected throughput for
> each station.
>
> It will be a generic mac80211 implementation. If the driver has
> get_expected_throughput implementation, it will be used instead.
>
> Useful for L2 routing protocols, like B.A.T.M.A.N.
>
> Signed-off-by: Baligh Gasmi <gasmibal@xxxxxxxxx>
> ---
> net/mac80211/driver-ops.h | 2 ++
> net/mac80211/sta_info.h | 2 ++
> net/mac80211/status.c | 22 ++++++++++++++++++++++
> net/mac80211/tx.c | 3 ++-
> 4 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/net/mac80211/driver-ops.h b/net/mac80211/driver-ops.h
> index 4e2fc1a08681..4331b79647fa 100644
> --- a/net/mac80211/driver-ops.h
> +++ b/net/mac80211/driver-ops.h
> @@ -1142,6 +1142,8 @@ static inline u32 drv_get_expected_throughput(struct ieee80211_local *local,
> trace_drv_get_expected_throughput(&sta->sta);
> if (local->ops->get_expected_throughput && sta->uploaded)
> ret = local->ops->get_expected_throughput(&local->hw, &sta->sta);
> + else
> + ret = ewma_avg_est_tp_read(&sta->status_stats.avg_est_tp);
> trace_drv_return_u32(local, ret);
>
> return ret;
> diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
> index 379fd367197f..fe60be4c671d 100644
> --- a/net/mac80211/sta_info.h
> +++ b/net/mac80211/sta_info.h
> @@ -123,6 +123,7 @@ enum ieee80211_sta_info_flags {
> #define HT_AGG_STATE_STOP_CB 7
> #define HT_AGG_STATE_SENT_ADDBA 8
>
> +DECLARE_EWMA(avg_est_tp, 8, 16)
> DECLARE_EWMA(avg_signal, 10, 8)
> enum ieee80211_agg_stop_reason {
> AGG_STOP_DECLINED,
> @@ -641,6 +642,7 @@ struct sta_info {
> s8 last_ack_signal;
> bool ack_signal_filled;
> struct ewma_avg_signal avg_ack_signal;
> + struct ewma_avg_est_tp avg_est_tp;
> } status_stats;
>
> /* Updated from TX path only, no locking requirements */
> diff --git a/net/mac80211/status.c b/net/mac80211/status.c
> index e81e8a5bb774..647ade3719f5 100644
> --- a/net/mac80211/status.c
> +++ b/net/mac80211/status.c
> @@ -1145,6 +1145,28 @@ void ieee80211_tx_status_ext(struct ieee80211_hw *hw,
> sta->status_stats.retry_failed++;
> sta->status_stats.retry_count += retry_count;
>
> + if (skb && tx_time_est) {
Shouldn't this be conditioned on actually being used (i.e., existence of
get_expected_throughput op? Also maybe pull it out into its own function
to make it clear what it's doing...
It's already the case I think, since the tx_time_est is not-zero only
when actually an estimated time is set.
A dedicated function seems good for me, for clarity, yes.
> + /* max average packet size */
> + size_t pkt_size = skb->len > 1024 ? 1024 : skb->len;
> +
> + if (acked) {
> + /* ACK packet size */
> + pkt_size += 14;
> + /* SIFS x 2 */
> + tx_time_est += 2 * 2;
> + }
> +
> + /* Backoff average x retries */
> + tx_time_est += retry_count ? retry_count * 2 : 2;
> +
> + /* failed tx */
> + if (!acked && !noack_success)
> + pkt_size = 0;
> +
> + ewma_avg_est_tp_add(&sta->status_stats.avg_est_tp,
> + ((pkt_size * 8) * 1000) / tx_time_est);
Could we avoid adding this division in the fast path?
Maybe we can use the do_div() macro for optimization, I don't see how
we can avoid it.
Here's one idea on how to make it less expensive and improve the average
of the throughput estimation at the same time:
In sta->status_stats add these fields:
u32 last_tp_update;
u32 pkt_size;
u32 tx_time_est;
And in this part of the code you do something like this:
u32 diff = ((u32)jiffies) - sta->status_stats.last_tp_update;
sta->status_stats.pkt_size += (pkt_size * 8) * 1000;
sta->status_stats.tx_time_est += tx_time_est;
if (diff > HZ / 10) {
ewma_avg_est_tp_add(&sta->status_stats.avg_est_tp,
sta->status_stats.pkt_size /
sta->status_stats.tx_time_est);
sta->status_stats.pkt_size = 0;
sta->status_stats.tx_time_est = 0;
}
This ensures that you will only get max. 1 update per 100ms interval.
Does that make sense?
- Felix
