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

[Kan Yan <kyan@google.com>]

> > 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 :)

Sounds good. The current default limits are reasonably conservative
and are tunable via debugfs.

I will give the v10 version of this patch serial a quick test and
hopefully we can wrap it up soon.

-Kan


On Sat, Nov 16, 2019 at 3:55 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> 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
>