Re: [PATCH v9 4/4] mac80211: Use Airtime-based Queue Limits (AQL) on packet dequeue

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Kan Yan <kyan@google.com> writes:

>> +static inline u16
>> +ieee80211_info_set_tx_time_est(struct ieee80211_tx_info *info, u16 tx_time_est)
>> +{
>> +       /* We only have 10 bits in tx_time_est, so store airtime
>> +        * in increments of 4us and clamp the maximum to 2**12-1
>> +        */
>> +       info->tx_time_est = min_t(u16, tx_time_est, 4095) >> 2;
>> +       return info->tx_time_est;
>> +}
>> +
>> +static inline u16
>> +ieee80211_info_get_tx_time_est(struct ieee80211_tx_info *info)
>> +{
>> +       return info->tx_time_est << 2;
>> +}
>> +
>
> set_tx_time_est() returns airtime in different units (4us) than
> get_tx_time_est(), this will cause the pending_airtime out of whack.

Huh, you're quite right; oops! I meant to shift that back before
returning. Will fix.

> Given the fact that AQL is only tested in very limited platforms,
> should we set the default to disabled by removing this change in the
> next update?
>
> -       local->airtime_flags = AIRTIME_USE_TX | AIRTIME_USE_RX;
> +
> +       local->airtime_flags = AIRTIME_USE_TX |
> +                              AIRTIME_USE_RX |
> +                              AIRTIME_USE_AQL;
> +       local->aql_threshold = IEEE80211_AQL_THRESHOLD;
> +       atomic_set(&local->aql_total_pending_airtime, 0);

Well, we have the whole -rc series to get more testing in if we merge it
as-is. It's up to the maintainers, of course, but I would be in favour
of merging as-is, then optionally backing out the default before the
final release if problems do turn up. But I would hope that the limits
are sufficiently conservative that it would not result in any problems :)

-Toke