Re: [PATCH V3 4/4] mac80211: Sync airtime weight sum with per AC synced sta airtime weight together

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

Yibo Zhao <yiboz@codeaurora.org> writes:

> Global airtime weight sum is updated only when txq is added/removed
> from rbtree. If upper layer configures sta weight during high load,
> airtime weight sum will not be updated since txq is most likely on the
> tree. It could a little late for upper layer to reconfigure sta weight
> when txq is already in the rbtree. And thus, incorrect airtime weight sum
> will lead to incorrect global virtual time calculation as well as overflow
> of airtime weight sum during txq removed.
>
> Hence, need to update airtime weight sum upon receiving event for
> configuring sta weight once sta's txq is on the rbtree.
>
> Besides, if airtime weight sum of ACs and sta weight is synced under the
> same per AC lock protection, there can be a very short window causing
> incorrct airtime weight sum calculation as below:
>
>     active_txq_lock_VO                          .
>     VO weight sum is syncd			.
>     sta airtime weight sum is synced		.
>     active_txq_unlock_VO			.
>     .						.
>     active_txq_lock_VI    			.
>     VI weight sum is syncd			.
>     sta airtime weight sum		active_txq_lock_BE
>     active_txq_unlock_VI	      Remove txq and thus sum
>     .				      is calculated with synced
>     .				      sta airtime weight
>     .					active_txq_unlock_BE
>
> So introduce a per ac synced station airtime weight synced with per
> AC synced weight sum together. And the per-AC station airtime weight
> is used to calculate weight sum.
>
> Signed-off-by: Yibo Zhao <yiboz@codeaurora.org>
> ---
>  net/mac80211/cfg.c         | 29 ++++++++++++++++++++++++++---
>  net/mac80211/debugfs_sta.c |  2 +-
>  net/mac80211/sta_info.c    |  9 ++++-----
>  net/mac80211/sta_info.h    |  5 +++--
>  net/mac80211/tx.c          |  4 ++--
>  5 files changed, 36 insertions(+), 13 deletions(-)
>
> diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
> index d65aa01..c8a0683 100644
> --- a/net/mac80211/cfg.c
> +++ b/net/mac80211/cfg.c
> @@ -1284,7 +1284,8 @@ static int sta_apply_parameters(struct ieee80211_local *local,
>  	int ret = 0;
>  	struct ieee80211_supported_band *sband;
>  	struct ieee80211_sub_if_data *sdata = sta->sdata;
> -	u32 mask, set;
> +	u32 mask, set, tid, ac, pre_weight;
> +	struct txq_info *txqi;
>  
>  	sband = ieee80211_get_sband(sdata);
>  	if (!sband)
> @@ -1452,8 +1453,30 @@ static int sta_apply_parameters(struct ieee80211_local *local,
>  	if (ieee80211_vif_is_mesh(&sdata->vif))
>  		sta_apply_mesh_params(local, sta, params);
>  
> -	if (params->airtime_weight)
> -		sta->airtime_weight = params->airtime_weight;
> +	if (params->airtime_weight &&
> +	    params->airtime_weight != sta->airtime_weight) {

This check doesn't work I think? You're not using the array-based
sta->airtime_weight[], and there are locking issues by just checking
like this; so maybe just keep the if() on params->airtime_weight, and do
the checking inside the loop while holding the lock?

Or could we just turn the weights into atomics to avoid the locking
entirely?

> +		for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
> +			spin_lock_bh(&local->active_txq_lock[ac]);
> +			for (tid = 0; tid < IEEE80211_NUM_TIDS + 1; tid++) {
> +				if (!sta->sta.txq[tid] ||
> +				    ac != ieee80211_ac_from_tid(tid))
> +					continue;
> +
> +				pre_weight = sta->airtime_weight[ac];
> +				sta->airtime_weight[ac] =
> +						params->airtime_weight;
> +
> +				txqi = to_txq_info(sta->sta.txq[tid]);
> +				if (RB_EMPTY_NODE(&txqi->schedule_order))
> +					continue;
> +
> +				local->airtime_weight_sum[ac] = local->airtime_weight_sum[ac] +
> +								params->airtime_weight -
> +								pre_weight;
> +			}
> +			spin_unlock_bh(&local->active_txq_lock[ac]);
> +		}
> +	}
>  
>  	/* set the STA state after all sta info from usermode has been set */
>  	if (test_sta_flag(sta, WLAN_STA_TDLS_PEER) ||
> diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
> index 80028da..43a7e6a 100644
> --- a/net/mac80211/debugfs_sta.c
> +++ b/net/mac80211/debugfs_sta.c
> @@ -223,7 +223,7 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
>  		"Virt-T: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n",
>  		rx_airtime,
>  		tx_airtime,
> -		sta->airtime_weight,
> +		sta->airtime_weight[0],
>  		v_t[0],
>  		v_t[1],
>  		v_t[2],
> diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
> index feac975..e599cf1 100644
> --- a/net/mac80211/sta_info.c
> +++ b/net/mac80211/sta_info.c
> @@ -384,11 +384,10 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
>  	if (sta_prepare_rate_control(local, sta, gfp))
>  		goto free_txq;
>  
> -	sta->airtime_weight = IEEE80211_DEFAULT_AIRTIME_WEIGHT;
> -
>  	for (i = 0; i < IEEE80211_NUM_ACS; i++) {
>  		skb_queue_head_init(&sta->ps_tx_buf[i]);
>  		skb_queue_head_init(&sta->tx_filtered[i]);
> +		sta->airtime_weight[i] = IEEE80211_DEFAULT_AIRTIME_WEIGHT;
>  	}
>  
>  	for (i = 0; i < IEEE80211_NUM_TIDS; i++)
> @@ -1850,11 +1849,11 @@ void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
>  	sta->airtime[ac].tx_airtime += tx_airtime;
>  	sta->airtime[ac].rx_airtime += rx_airtime;
>  
> -	weight_sum = local->airtime_weight_sum[ac] ?: sta->airtime_weight;
> +	weight_sum = local->airtime_weight_sum[ac] ?: sta->airtime_weight[ac];
>  
>  	/* Round the calculation of global vt */
>  	local->airtime_v_t[ac] += (airtime + (weight_sum >> 1)) / weight_sum;
> -	sta->airtime[ac].v_t += airtime / sta->airtime_weight;
> +	sta->airtime[ac].v_t += airtime / sta->airtime_weight[ac];
>  	ieee80211_resort_txq(&local->hw, txq);
>  
>  	spin_unlock_bh(&local->active_txq_lock[ac]);
> @@ -2236,7 +2235,7 @@ void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo,
>  	}
>  
>  	if (!(sinfo->filled & BIT_ULL(NL80211_STA_INFO_AIRTIME_WEIGHT))) {
> -		sinfo->airtime_weight = sta->airtime_weight;
> +		sinfo->airtime_weight = sta->airtime_weight[0];
>  		sinfo->filled |= BIT_ULL(NL80211_STA_INFO_AIRTIME_WEIGHT);
>  	}
>  
> diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
> index 5055f94..2697343 100644
> --- a/net/mac80211/sta_info.h
> +++ b/net/mac80211/sta_info.h
> @@ -476,7 +476,8 @@ struct ieee80211_sta_rx_stats {
>   * @tid_seq: per-TID sequence numbers for sending to this STA
>   * @airtime: per-AC struct airtime_info describing airtime statistics for this
>   *	station
> - * @airtime_weight: station weight for airtime fairness calculation purposes
> + * @airtime_weight: station per-AC weight for airtime fairness calculation
> + * purposes
>   * @ampdu_mlme: A-MPDU state machine state
>   * @mesh: mesh STA information
>   * @debugfs_dir: debug filesystem directory dentry
> @@ -602,7 +603,7 @@ struct sta_info {
>  	u16 tid_seq[IEEE80211_QOS_CTL_TID_MASK + 1];
>  
>  	struct airtime_info airtime[IEEE80211_NUM_ACS];
> -	u16 airtime_weight;
> +	u16 airtime_weight[IEEE80211_NUM_ACS];
>  
>  	/*
>  	 * Aggregation information, locked with lock.
> diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
> index 60cf569..286cf14 100644
> --- a/net/mac80211/tx.c
> +++ b/net/mac80211/tx.c
> @@ -3735,7 +3735,7 @@ void ieee80211_schedule_txq(struct ieee80211_hw *hw,
>  		struct sta_info *sta = container_of(txq->sta,
>  						    struct sta_info, sta);
>  
> -		local->airtime_weight_sum[ac] += sta->airtime_weight;
> +		local->airtime_weight_sum[ac] += sta->airtime_weight[ac];
>  		if (local->airtime_v_t[ac] > AIRTIME_GRACE)
>  			sta->airtime[ac].v_t = max(local->airtime_v_t[ac] - AIRTIME_GRACE,
>  						   sta->airtime[ac].v_t);
> @@ -3779,7 +3779,7 @@ static void __ieee80211_unschedule_txq(struct ieee80211_hw *hw,
>  		struct sta_info *sta = container_of(txq->sta,
>  						    struct sta_info, sta);
>  
> -		local->airtime_weight_sum[ac] -= sta->airtime_weight;
> +		local->airtime_weight_sum[ac] -= sta->airtime_weight[ac];
>  	}
>  
>  	rb_erase_cached(&txqi->schedule_order,
> -- 
> 1.9.1


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