| Message ID | 157115994190.2500430.14955682016008497593.stgit@toke.dk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add Airtime Queue Limits (AQL) to mac80211 | expand |
Hi Toke, Thanks for getting this done! I will give it a try in the next few days. A few comments: > The estimated airtime for each skb is stored in the tx_info, so we can > subtract the same amount from the running total when the skb is freed or > recycled. Looks like ath10k driver zero out the info->status before calling ieee80211_tx_status(...): int ath10k_txrx_tx_unref(struct ath10k_htt *htt, const struct htt_tx_done *tx_done) { ... info = IEEE80211_SKB_CB(msdu); memset(&info->status, 0, sizeof(info->status)); ... ieee80211_tx_status(htt->ar->hw, msdu); } We need either restore the info->status.tx_time_est or calling ieee80211_sta_update_pending_airtime() in ath10k before tx_time_est get erased. > + if (local->airtime_flags & AIRTIME_USE_AQL) { > + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, > + skb->len + 38); I think it is better to put the "+ 38" that takes care of the header overhead inside ieee80211_calc_expected_tx_airtime(). Kan On Tue, Oct 15, 2019 at 10:19 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote: > > From: Toke Høiland-Jørgensen <toke@redhat.com> > > The previous commit added the ability to throttle stations when they queue > too much airtime in the hardware. This commit enables the functionality by > calculating the expected airtime usage of each packet that is dequeued from > the TXQs in mac80211, and accounting that as pending airtime. > > The estimated airtime for each skb is stored in the tx_info, so we can > subtract the same amount from the running total when the skb is freed or > recycled. The throttling mechanism relies on this accounting to be > accurate (i.e., that we are not freeing skbs without subtracting any > airtime they were accounted for), so we put the subtraction into > ieee80211_report_used_skb(). As an optimisation, we also subtract the > airtime on regular TX completion, zeroing out the value stored in the > packet afterwards, to avoid having to do an expensive lookup of the > station from the packet data on every packet. > > This patch does *not* include any mechanism to wake a throttled TXQ again, > on the assumption that this will happen anyway as a side effect of whatever > freed the skb (most commonly a TX completion). > > Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> > --- > net/mac80211/status.c | 38 ++++++++++++++++++++++++++++++++++++++ > net/mac80211/tx.c | 16 ++++++++++++++++ > 2 files changed, 54 insertions(+) > > diff --git a/net/mac80211/status.c b/net/mac80211/status.c > index ab8ba5835ca0..ce990a1e9043 100644 > --- a/net/mac80211/status.c > +++ b/net/mac80211/status.c > @@ -676,6 +676,33 @@ static void ieee80211_report_used_skb(struct ieee80211_local *local, > if (dropped) > acked = false; > > + if (info->status.tx_time_est) { > + struct ieee80211_sub_if_data *sdata; > + struct sta_info *sta = NULL; > + u8 *qc, ac; > + int tid; > + > + rcu_read_lock(); > + > + sdata = ieee80211_sdata_from_skb(local, skb); > + if (sdata) > + sta = sta_info_get_bss(sdata, skb_mac_header(skb)); > + > + if (ieee80211_is_data_qos(hdr->frame_control)) { > + qc = ieee80211_get_qos_ctl(hdr); > + tid = qc[0] & 0xf; > + ac = ieee80211_ac_from_tid(tid); > + } else { > + ac = IEEE80211_AC_BE; > + } > + > + ieee80211_sta_update_pending_airtime(local, sta, ac, > + info->status.tx_time_est, > + true); > + rcu_read_unlock(); > + > + } > + > if (info->flags & IEEE80211_TX_INTFL_MLME_CONN_TX) { > struct ieee80211_sub_if_data *sdata; > > @@ -930,6 +957,17 @@ static void __ieee80211_tx_status(struct ieee80211_hw *hw, > tid = qc[0] & 0xf; > } > > + if (info->status.tx_time_est) { > + /* Do this here to avoid the expensive lookup of the sta > + * in ieee80211_report_used_skb(). > + */ > + ieee80211_sta_update_pending_airtime(local, sta, > + ieee80211_ac_from_tid(tid), > + info->status.tx_time_est, > + true); > + info->status.tx_time_est = 0; > + } > + > if (!acked && ieee80211_is_back_req(fc)) { > u16 control; > > diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c > index 405f622b3fe0..b6b47171b340 100644 > --- a/net/mac80211/tx.c > +++ b/net/mac80211/tx.c > @@ -3539,9 +3539,14 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw, > struct ieee80211_tx_data tx; > ieee80211_tx_result r; > struct ieee80211_vif *vif = txq->vif; > + u8 ac = txq->ac; > + u32 airtime; > > WARN_ON_ONCE(softirq_count() == 0); > > + if (!ieee80211_txq_airtime_check(hw, txq)) > + return NULL; > + > begin: > spin_lock_bh(&fq->lock); > > @@ -3652,6 +3657,17 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw, > } > > IEEE80211_SKB_CB(skb)->control.vif = vif; > + > + if (local->airtime_flags & AIRTIME_USE_AQL) { > + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, > + skb->len + 38); > + if (airtime) { > + info->control.tx_time_est = airtime; > + ieee80211_sta_update_pending_airtime(local, tx.sta, ac, > + airtime, false); > + } > + } > + > return skb; > > out: >
Kan Yan <kyan@google.com> writes: > Hi Toke, > > Thanks for getting this done! I will give it a try in the next few > days. A few comments: > >> The estimated airtime for each skb is stored in the tx_info, so we can >> subtract the same amount from the running total when the skb is freed or >> recycled. > > Looks like ath10k driver zero out the info->status before calling > ieee80211_tx_status(...): > int ath10k_txrx_tx_unref(struct ath10k_htt *htt, > const struct htt_tx_done *tx_done) > { > ... > info = IEEE80211_SKB_CB(msdu); > memset(&info->status, 0, sizeof(info->status)); > ... > ieee80211_tx_status(htt->ar->hw, msdu); > } Ah, bugger; I was afraid we'd run into this. A quick grep indicates that it's only ath10k and iwl that do this, though, so it's probably manageable to just fix this. I think the simplest solution is just to restore the field after clearing, no? > We need either restore the info->status.tx_time_est or calling > ieee80211_sta_update_pending_airtime() in ath10k before tx_time_est > get erased. > >> + if (local->airtime_flags & AIRTIME_USE_AQL) { >> + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, >> + skb->len + 38); > > I think it is better to put the "+ 38" that takes care of the header > overhead inside ieee80211_calc_expected_tx_airtime(). Hmm, no strong opinion about this; but yeah, since we have a dedicated function for this use I guess there's no harm in adding it there :) -Toke
> On Oct 17, 2019, at 11:44, Toke Høiland-Jørgensen <toke@redhat.com> wrote: > > Kan Yan <kyan@google.com> writes: > >> Hi Toke, >> >> Thanks for getting this done! I will give it a try in the next few >> days. A few comments: >> >>> The estimated airtime for each skb is stored in the tx_info, so we can >>> subtract the same amount from the running total when the skb is freed or >>> recycled. >> >> Looks like ath10k driver zero out the info->status before calling >> ieee80211_tx_status(...): >> int ath10k_txrx_tx_unref(struct ath10k_htt *htt, >> const struct htt_tx_done *tx_done) >> { >> ... >> info = IEEE80211_SKB_CB(msdu); >> memset(&info->status, 0, sizeof(info->status)); >> ... >> ieee80211_tx_status(htt->ar->hw, msdu); >> } > > Ah, bugger; I was afraid we'd run into this. A quick grep indicates that > it's only ath10k and iwl that do this, though, so it's probably > manageable to just fix this. I think the simplest solution is just to > restore the field after clearing, no? > >> We need either restore the info->status.tx_time_est or calling >> ieee80211_sta_update_pending_airtime() in ath10k before tx_time_est >> get erased. >> >>> + if (local->airtime_flags & AIRTIME_USE_AQL) { >>> + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, >>> + skb->len + 38); >> >> I think it is better to put the "+ 38" that takes care of the header >> overhead inside ieee80211_calc_expected_tx_airtime(). > > Hmm, no strong opinion about this; but yeah, since we have a dedicated > function for this use I guess there's no harm in adding it there :) > Silly question, is this Overhead guaranteed to be 38 Bytes for all eternity? Otherwise a variable or a preprocessor constant might be more future proof? Best Regards Sebastian > -Toke > > _______________________________________________ > Make-wifi-fast mailing list > Make-wifi-fast@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/make-wifi-fast
Sebastian Moeller <moeller0@gmx.de> writes: >> On Oct 17, 2019, at 11:44, Toke Høiland-Jørgensen <toke@redhat.com> wrote: >> >> Kan Yan <kyan@google.com> writes: >> >>> Hi Toke, >>> >>> Thanks for getting this done! I will give it a try in the next few >>> days. A few comments: >>> >>>> The estimated airtime for each skb is stored in the tx_info, so we can >>>> subtract the same amount from the running total when the skb is freed or >>>> recycled. >>> >>> Looks like ath10k driver zero out the info->status before calling >>> ieee80211_tx_status(...): >>> int ath10k_txrx_tx_unref(struct ath10k_htt *htt, >>> const struct htt_tx_done *tx_done) >>> { >>> ... >>> info = IEEE80211_SKB_CB(msdu); >>> memset(&info->status, 0, sizeof(info->status)); >>> ... >>> ieee80211_tx_status(htt->ar->hw, msdu); >>> } >> >> Ah, bugger; I was afraid we'd run into this. A quick grep indicates that >> it's only ath10k and iwl that do this, though, so it's probably >> manageable to just fix this. I think the simplest solution is just to >> restore the field after clearing, no? >> >>> We need either restore the info->status.tx_time_est or calling >>> ieee80211_sta_update_pending_airtime() in ath10k before tx_time_est >>> get erased. >>> >>>> + if (local->airtime_flags & AIRTIME_USE_AQL) { >>>> + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, >>>> + skb->len + 38); >>> >>> I think it is better to put the "+ 38" that takes care of the header >>> overhead inside ieee80211_calc_expected_tx_airtime(). >> >> Hmm, no strong opinion about this; but yeah, since we have a dedicated >> function for this use I guess there's no harm in adding it there :) >> > > Silly question, is this Overhead guaranteed to be 38 Bytes for all > eternity? Otherwise a variable or a preprocessor constant might be > more future proof? Well, yeah, as long as we're sending Ethernet packets. Which is kinda baked into the WiFi standard :) -Toke
What about VLAN tags? Best Regards Sebastian > On Oct 17, 2019, at 12:24, Toke Høiland-Jørgensen <toke@redhat.com> wrote: > > Sebastian Moeller <moeller0@gmx.de> writes: > >>> On Oct 17, 2019, at 11:44, Toke Høiland-Jørgensen <toke@redhat.com> wrote: >>> >>> Kan Yan <kyan@google.com> writes: >>> >>>> Hi Toke, >>>> >>>> Thanks for getting this done! I will give it a try in the next few >>>> days. A few comments: >>>> >>>>> The estimated airtime for each skb is stored in the tx_info, so we can >>>>> subtract the same amount from the running total when the skb is freed or >>>>> recycled. >>>> >>>> Looks like ath10k driver zero out the info->status before calling >>>> ieee80211_tx_status(...): >>>> int ath10k_txrx_tx_unref(struct ath10k_htt *htt, >>>> const struct htt_tx_done *tx_done) >>>> { >>>> ... >>>> info = IEEE80211_SKB_CB(msdu); >>>> memset(&info->status, 0, sizeof(info->status)); >>>> ... >>>> ieee80211_tx_status(htt->ar->hw, msdu); >>>> } >>> >>> Ah, bugger; I was afraid we'd run into this. A quick grep indicates that >>> it's only ath10k and iwl that do this, though, so it's probably >>> manageable to just fix this. I think the simplest solution is just to >>> restore the field after clearing, no? >>> >>>> We need either restore the info->status.tx_time_est or calling >>>> ieee80211_sta_update_pending_airtime() in ath10k before tx_time_est >>>> get erased. >>>> >>>>> + if (local->airtime_flags & AIRTIME_USE_AQL) { >>>>> + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, >>>>> + skb->len + 38); >>>> >>>> I think it is better to put the "+ 38" that takes care of the header >>>> overhead inside ieee80211_calc_expected_tx_airtime(). >>> >>> Hmm, no strong opinion about this; but yeah, since we have a dedicated >>> function for this use I guess there's no harm in adding it there :) >>> >> >> Silly question, is this Overhead guaranteed to be 38 Bytes for all >> eternity? Otherwise a variable or a preprocessor constant might be >> more future proof? > > Well, yeah, as long as we're sending Ethernet packets. Which is kinda > baked into the WiFi standard :) > > -Toke
I don't think it is hard to take care of extra header size for frames with VLAN tags, but the question is how far are we willing to go down this rabbit hole. There are other factors like retries and aggregation that are difficult to be taken into account. However, I doubt that matters, a ballpark estimate of airtime is sufficient for the purpose of implementing a queue limit. On Thu, Oct 17, 2019 at 3:25 AM Sebastian Moeller <moeller0@gmx.de> wrote: > > What about VLAN tags? > > Best Regards > Sebastian > > > On Oct 17, 2019, at 12:24, Toke Høiland-Jørgensen <toke@redhat.com> wrote: > > > > Sebastian Moeller <moeller0@gmx.de> writes: > > > >>> On Oct 17, 2019, at 11:44, Toke Høiland-Jørgensen <toke@redhat.com> wrote: > >>> > >>> Kan Yan <kyan@google.com> writes: > >>> > >>>> Hi Toke, > >>>> > >>>> Thanks for getting this done! I will give it a try in the next few > >>>> days. A few comments: > >>>> > >>>>> The estimated airtime for each skb is stored in the tx_info, so we can > >>>>> subtract the same amount from the running total when the skb is freed or > >>>>> recycled. > >>>> > >>>> Looks like ath10k driver zero out the info->status before calling > >>>> ieee80211_tx_status(...): > >>>> int ath10k_txrx_tx_unref(struct ath10k_htt *htt, > >>>> const struct htt_tx_done *tx_done) > >>>> { > >>>> ... > >>>> info = IEEE80211_SKB_CB(msdu); > >>>> memset(&info->status, 0, sizeof(info->status)); > >>>> ... > >>>> ieee80211_tx_status(htt->ar->hw, msdu); > >>>> } > >>> > >>> Ah, bugger; I was afraid we'd run into this. A quick grep indicates that > >>> it's only ath10k and iwl that do this, though, so it's probably > >>> manageable to just fix this. I think the simplest solution is just to > >>> restore the field after clearing, no? > >>> > >>>> We need either restore the info->status.tx_time_est or calling > >>>> ieee80211_sta_update_pending_airtime() in ath10k before tx_time_est > >>>> get erased. > >>>> > >>>>> + if (local->airtime_flags & AIRTIME_USE_AQL) { > >>>>> + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, > >>>>> + skb->len + 38); > >>>> > >>>> I think it is better to put the "+ 38" that takes care of the header > >>>> overhead inside ieee80211_calc_expected_tx_airtime(). > >>> > >>> Hmm, no strong opinion about this; but yeah, since we have a dedicated > >>> function for this use I guess there's no harm in adding it there :) > >>> > >> > >> Silly question, is this Overhead guaranteed to be 38 Bytes for all > >> eternity? Otherwise a variable or a preprocessor constant might be > >> more future proof? > > > > Well, yeah, as long as we're sending Ethernet packets. Which is kinda > > baked into the WiFi standard :) > > > > -Toke >
On Thu, 2019-10-17 at 18:11 -0700, Kan Yan wrote: > I don't think it is hard to take care of extra header size for frames > with VLAN tags VLAN tags are payload as far as wifi is concerned, so no need to take that into account ... johannes
diff --git a/net/mac80211/status.c b/net/mac80211/status.c index ab8ba5835ca0..ce990a1e9043 100644 --- a/net/mac80211/status.c +++ b/net/mac80211/status.c @@ -676,6 +676,33 @@ static void ieee80211_report_used_skb(struct ieee80211_local *local, if (dropped) acked = false; + if (info->status.tx_time_est) { + struct ieee80211_sub_if_data *sdata; + struct sta_info *sta = NULL; + u8 *qc, ac; + int tid; + + rcu_read_lock(); + + sdata = ieee80211_sdata_from_skb(local, skb); + if (sdata) + sta = sta_info_get_bss(sdata, skb_mac_header(skb)); + + if (ieee80211_is_data_qos(hdr->frame_control)) { + qc = ieee80211_get_qos_ctl(hdr); + tid = qc[0] & 0xf; + ac = ieee80211_ac_from_tid(tid); + } else { + ac = IEEE80211_AC_BE; + } + + ieee80211_sta_update_pending_airtime(local, sta, ac, + info->status.tx_time_est, + true); + rcu_read_unlock(); + + } + if (info->flags & IEEE80211_TX_INTFL_MLME_CONN_TX) { struct ieee80211_sub_if_data *sdata; @@ -930,6 +957,17 @@ static void __ieee80211_tx_status(struct ieee80211_hw *hw, tid = qc[0] & 0xf; } + if (info->status.tx_time_est) { + /* Do this here to avoid the expensive lookup of the sta + * in ieee80211_report_used_skb(). + */ + ieee80211_sta_update_pending_airtime(local, sta, + ieee80211_ac_from_tid(tid), + info->status.tx_time_est, + true); + info->status.tx_time_est = 0; + } + if (!acked && ieee80211_is_back_req(fc)) { u16 control; diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 405f622b3fe0..b6b47171b340 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -3539,9 +3539,14 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw, struct ieee80211_tx_data tx; ieee80211_tx_result r; struct ieee80211_vif *vif = txq->vif; + u8 ac = txq->ac; + u32 airtime; WARN_ON_ONCE(softirq_count() == 0); + if (!ieee80211_txq_airtime_check(hw, txq)) + return NULL; + begin: spin_lock_bh(&fq->lock); @@ -3652,6 +3657,17 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw, } IEEE80211_SKB_CB(skb)->control.vif = vif; + + if (local->airtime_flags & AIRTIME_USE_AQL) { + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, + skb->len + 38); + if (airtime) { + info->control.tx_time_est = airtime; + ieee80211_sta_update_pending_airtime(local, tx.sta, ac, + airtime, false); + } + } + return skb; out: