package/kernel/mac80211/patches/subsys/354-mac80211-calculate-hash-for-fq-without-holding-fq-lo.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Sat, 16 Mar 2019 17:57:38 +0100
   3 Subject: [PATCH] mac80211: calculate hash for fq without holding fq->lock
   4  in itxq enqueue
   5
   6 Reduces lock contention on enqueue/dequeue of iTXQ packets
   7
   8 Signed-off-by: Felix Fietkau <nbd@nbd.name>
   9 ---
  10
  11 --- a/include/net/fq_impl.h
  12 +++ b/include/net/fq_impl.h
  13 @@ -107,21 +107,23 @@ begin:
  14         return skb;
  15  }
  16
  17 +static u32 fq_flow_idx(struct fq *fq, struct sk_buff *skb)
  18 +{
  19 +       u32 hash = skb_get_hash_perturb(skb, fq->perturbation);
  20 +
  21 +       return reciprocal_scale(hash, fq->flows_cnt);
  22 +}
  23 +
  24  static struct fq_flow *fq_flow_classify(struct fq *fq,
  25 -                                       struct fq_tin *tin,
  26 +                                       struct fq_tin *tin, u32 idx,
  27                                         struct sk_buff *skb,
  28                                         fq_flow_get_default_t get_default_func)
  29  {
  30         struct fq_flow *flow;
  31 -       u32 hash;
  32 -       u32 idx;
  33
  34         lockdep_assert_held(&fq->lock);
  35
  36 -       hash = skb_get_hash_perturb(skb, fq->perturbation);
  37 -       idx = reciprocal_scale(hash, fq->flows_cnt);
  38         flow = &fq->flows[idx];
  39 -
  40         if (flow->tin && flow->tin != tin) {
  41                 flow = get_default_func(fq, tin, idx, skb);
  42                 tin->collisions++;
  43 @@ -153,7 +155,7 @@ static void fq_recalc_backlog(struct fq
  44  }
  45
  46  static void fq_tin_enqueue(struct fq *fq,
  47 -                          struct fq_tin *tin,
  48 +                          struct fq_tin *tin, u32 idx,
  49                            struct sk_buff *skb,
  50                            fq_skb_free_t free_func,
  51                            fq_flow_get_default_t get_default_func)
  52 @@ -163,7 +165,7 @@ static void fq_tin_enqueue(struct fq *fq
  53
  54         lockdep_assert_held(&fq->lock);
  55
  56 -       flow = fq_flow_classify(fq, tin, skb, get_default_func);
  57 +       flow = fq_flow_classify(fq, tin, idx, skb, get_default_func);
  58
  59         flow->tin = tin;
  60         flow->backlog += skb->len;
  61 --- a/net/mac80211/tx.c
  62 +++ b/net/mac80211/tx.c
  63 @@ -1390,11 +1390,15 @@ static void ieee80211_txq_enqueue(struct
  64  {
  65         struct fq *fq = &local->fq;
  66         struct fq_tin *tin = &txqi->tin;
  67 +       u32 flow_idx = fq_flow_idx(fq, skb);
  68
  69         ieee80211_set_skb_enqueue_time(skb);
  70 -       fq_tin_enqueue(fq, tin, skb,
  71 +
  72 +       spin_lock_bh(&fq->lock);
  73 +       fq_tin_enqueue(fq, tin, flow_idx, skb,
  74                        fq_skb_free_func,
  75                        fq_flow_get_default_func);
  76 +       spin_unlock_bh(&fq->lock);
  77  }
  78
  79  static bool fq_vlan_filter_func(struct fq *fq, struct fq_tin *tin,
  80 @@ -1564,7 +1568,6 @@ static bool ieee80211_queue_skb(struct i
  81                                 struct sta_info *sta,
  82                                 struct sk_buff *skb)
  83  {
  84 -       struct fq *fq = &local->fq;
  85         struct ieee80211_vif *vif;
  86         struct txq_info *txqi;
  87
  88 @@ -1582,9 +1585,7 @@ static bool ieee80211_queue_skb(struct i
  89         if (!txqi)
  90                 return false;
  91
  92 -       spin_lock_bh(&fq->lock);
  93         ieee80211_txq_enqueue(local, txqi, skb);
  94 -       spin_unlock_bh(&fq->lock);
  95
  96         schedule_and_wake_txq(local, txqi);
  97
  98 @@ -3198,6 +3199,7 @@ static bool ieee80211_amsdu_aggregate(st
  99         u8 max_subframes = sta->sta.max_amsdu_subframes;
 100         int max_frags = local->hw.max_tx_fragments;
 101         int max_amsdu_len = sta->sta.max_amsdu_len;
 102 +       u32 flow_idx;
 103         int orig_truesize;
 104         __be16 len;
 105         void *data;
 106 @@ -3220,6 +3222,8 @@ static bool ieee80211_amsdu_aggregate(st
 107                 max_amsdu_len = min_t(int, max_amsdu_len,
 108                                       sta->sta.max_rc_amsdu_len);
 109
 110 +       flow_idx = fq_flow_idx(fq, skb);
 111 +
 112         spin_lock_bh(&fq->lock);
 113
 114         /* TODO: Ideally aggregation should be done on dequeue to remain
 115 @@ -3227,7 +3231,8 @@ static bool ieee80211_amsdu_aggregate(st
 116          */
 117
 118         tin = &txqi->tin;
 119 -       flow = fq_flow_classify(fq, tin, skb, fq_flow_get_default_func);
 120 +       flow = fq_flow_classify(fq, tin, flow_idx, skb,
 121 +                               fq_flow_get_default_func);
 122         head = skb_peek_tail(&flow->queue);
 123         if (!head)
 124                 goto unlock;