package/kernel/mac80211/patches/333-cfg80211-reuse-existing-page-fragments-in-A-MSDU-rx.patch

   1 From: Felix Fietkau <nbd@openwrt.org>
   2 Date: Mon, 8 Feb 2016 14:33:19 +0100
   3 Subject: [PATCH] cfg80211: reuse existing page fragments in A-MSDU rx
   4
   5 This massively reduces data copying and thus improves rx performance
   6
   7 Signed-off-by: Felix Fietkau <nbd@openwrt.org>
   8 ---
   9
  10 --- a/net/wireless/util.c
  11 +++ b/net/wireless/util.c
  12 @@ -644,23 +644,93 @@ int ieee80211_data_from_8023(struct sk_b
  13  }
  14  EXPORT_SYMBOL(ieee80211_data_from_8023);
  15
  16 +static void
  17 +__frame_add_frag(struct sk_buff *skb, struct page *page,
  18 +                void *ptr, int len, int size)
  19 +{
  20 +       struct skb_shared_info *sh = skb_shinfo(skb);
  21 +       int page_offset;
  22 +
  23 +       atomic_inc(&page->_count);
  24 +       page_offset = ptr - page_address(page);
  25 +       skb_add_rx_frag(skb, sh->nr_frags, page, page_offset, len, size);
  26 +}
  27 +
  28 +static void
  29 +__ieee80211_amsdu_copy_frag(struct sk_buff *skb, struct sk_buff *frame,
  30 +                           int offset, int len)
  31 +{
  32 +       struct skb_shared_info *sh = skb_shinfo(skb);
  33 +       const skb_frag_t *frag = &sh->frags[-1];
  34 +       struct page *frag_page;
  35 +       void *frag_ptr;
  36 +       int frag_len, frag_size;
  37 +       int head_size = skb->len - skb->data_len;
  38 +       int cur_len;
  39 +
  40 +       frag_page = virt_to_head_page(skb->head);
  41 +       frag_ptr = skb->data;
  42 +       frag_size = head_size;
  43 +
  44 +       while (offset >= frag_size) {
  45 +               offset -= frag_size;
  46 +               frag++;
  47 +               frag_page = skb_frag_page(frag);
  48 +               frag_ptr = skb_frag_address(frag);
  49 +               frag_size = skb_frag_size(frag);
  50 +       }
  51 +
  52 +       frag_ptr += offset;
  53 +       frag_len = frag_size - offset;
  54 +
  55 +       cur_len = min(len, frag_len);
  56 +
  57 +       __frame_add_frag(frame, frag_page, frag_ptr, cur_len, frag_size);
  58 +       len -= cur_len;
  59 +
  60 +       while (len > 0) {
  61 +               frag++;
  62 +               frag_len = skb_frag_size(frag);
  63 +               cur_len = min(len, frag_len);
  64 +               __frame_add_frag(frame, skb_frag_page(frag),
  65 +                                skb_frag_address(frag), cur_len, frag_len);
  66 +               len -= cur_len;
  67 +       }
  68 +}
  69 +
  70  static struct sk_buff *
  71  __ieee80211_amsdu_copy(struct sk_buff *skb, unsigned int hlen,
  72 -                      int offset, int len)
  73 +                      int offset, int len, bool reuse_frag)
  74  {
  75         struct sk_buff *frame;
  76 +       int cur_len = len;
  77
  78         if (skb->len - offset < len)
  79                 return NULL;
  80
  81         /*
  82 +        * When reusing framents, copy some data to the head to simplify
  83 +        * ethernet header handling and speed up protocol header processing
  84 +        * in the stack later.
  85 +        */
  86 +       if (reuse_frag)
  87 +               cur_len = min_t(int, len, 32);
  88 +
  89 +       /*
  90          * Allocate and reserve two bytes more for payload
  91          * alignment since sizeof(struct ethhdr) is 14.
  92          */
  93 -       frame = dev_alloc_skb(hlen + sizeof(struct ethhdr) + 2 + len);
  94 +       frame = dev_alloc_skb(hlen + sizeof(struct ethhdr) + 2 + cur_len);
  95
  96         skb_reserve(frame, hlen + sizeof(struct ethhdr) + 2);
  97 -       skb_copy_bits(skb, offset, skb_put(frame, len), len);
  98 +       skb_copy_bits(skb, offset, skb_put(frame, cur_len), cur_len);
  99 +
 100 +       len -= cur_len;
 101 +       if (!len)
 102 +               return frame;
 103 +
 104 +       offset += cur_len;
 105 +       __ieee80211_amsdu_copy_frag(skb, frame, offset, len);
 106
 107         return frame;
 108  }
 109 @@ -676,6 +746,7 @@ void ieee80211_amsdu_to_8023s(struct sk_
 110         u8 *payload;
 111         int offset = 0, remaining, err;
 112         struct ethhdr eth;
 113 +       bool reuse_frag = skb->head_frag && !skb_has_frag_list(skb);
 114         bool reuse_skb = false;
 115         bool last = false;
 116
 117 @@ -703,12 +774,13 @@ void ieee80211_amsdu_to_8023s(struct sk_
 118                 offset += sizeof(struct ethhdr);
 119                 /* reuse skb for the last subframe */
 120                 last = remaining <= subframe_len + padding;
 121 -               if (!skb_is_nonlinear(skb) && last) {
 122 +               if (!skb_is_nonlinear(skb) && !reuse_frag && last) {
 123                         skb_pull(skb, offset);
 124                         frame = skb;
 125                         reuse_skb = true;
 126                 } else {
 127 -                       frame = __ieee80211_amsdu_copy(skb, hlen, offset, len);
 128 +                       frame = __ieee80211_amsdu_copy(skb, hlen, offset, len,
 129 +                                                      reuse_frag);
 130                         if (!frame)
 131                                 goto purge;
 132