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 <[email protected]>
>> > ---
>> > 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