mac80211: improve a-msdu rx performance by avoiding unnecessary data copying

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
SVN-Revision: 48673

diff --git a/package/kernel/mac80211/patches/333-cfg80211-reuse-existing-page-fragments-in-A-MSDU-rx.patch b/package/kernel/mac80211/patches/333-cfg80211-reuse-existing-page-fragments-in-A-MSDU-rx.patch
new file mode 100644 (file)
index 0000000..6e2d0cf
--- /dev/null
+++ b/package/kernel/mac80211/patches/333-cfg80211-reuse-existing-page-fragments-in-A-MSDU-rx.patch
@@ -0,0 +1,132 @@
+From: Felix Fietkau <nbd@openwrt.org>
+Date: Mon, 8 Feb 2016 14:33:19 +0100
+Subject: [PATCH] cfg80211: reuse existing page fragments in A-MSDU rx
+
+This massively reduces data copying and thus improves rx performance
+
+Signed-off-by: Felix Fietkau <nbd@openwrt.org>
+---
+
+--- a/net/wireless/util.c
++++ b/net/wireless/util.c
+@@ -644,23 +644,93 @@ int ieee80211_data_from_8023(struct sk_b
+ }
+ EXPORT_SYMBOL(ieee80211_data_from_8023);
+ 
++static void
++__frame_add_frag(struct sk_buff *skb, struct page *page,
++               void *ptr, int len, int size)
++{
++      struct skb_shared_info *sh = skb_shinfo(skb);
++      int page_offset;
++
++      atomic_inc(&page->_count);
++      page_offset = ptr - page_address(page);
++      skb_add_rx_frag(skb, sh->nr_frags, page, page_offset, len, size);
++}
++
++static void
++__ieee80211_amsdu_copy_frag(struct sk_buff *skb, struct sk_buff *frame,
++                          int offset, int len)
++{
++      struct skb_shared_info *sh = skb_shinfo(skb);
++      const skb_frag_t *frag = &sh->frags[-1];
++      struct page *frag_page;
++      void *frag_ptr;
++      int frag_len, frag_size;
++      int head_size = skb->len - skb->data_len;
++      int cur_len;
++
++      frag_page = virt_to_head_page(skb->head);
++      frag_ptr = skb->data;
++      frag_size = head_size;
++
++      while (offset >= frag_size) {
++              offset -= frag_size;
++              frag++;
++              frag_page = skb_frag_page(frag);
++              frag_ptr = skb_frag_address(frag);
++              frag_size = skb_frag_size(frag);
++      }
++
++      frag_ptr += offset;
++      frag_len = frag_size - offset;
++
++      cur_len = min(len, frag_len);
++
++      __frame_add_frag(frame, frag_page, frag_ptr, cur_len, frag_size);
++      len -= cur_len;
++
++      while (len > 0) {
++              frag++;
++              frag_len = skb_frag_size(frag);
++              cur_len = min(len, frag_len);
++              __frame_add_frag(frame, skb_frag_page(frag),
++                               skb_frag_address(frag), cur_len, frag_len);
++              len -= cur_len;
++      }
++}
++
+ static struct sk_buff *
+ __ieee80211_amsdu_copy(struct sk_buff *skb, unsigned int hlen,
+-                     int offset, int len)
++                     int offset, int len, bool reuse_frag)
+ {
+       struct sk_buff *frame;
++      int cur_len = len;
+ 
+       if (skb->len - offset < len)
+               return NULL;
+ 
+       /*
++       * When reusing framents, copy some data to the head to simplify
++       * ethernet header handling and speed up protocol header processing
++       * in the stack later.
++       */
++      if (reuse_frag)
++              cur_len = min_t(int, len, 32);
++
++      /*
+        * Allocate and reserve two bytes more for payload
+        * alignment since sizeof(struct ethhdr) is 14.
+        */
+-      frame = dev_alloc_skb(hlen + sizeof(struct ethhdr) + 2 + len);
++      frame = dev_alloc_skb(hlen + sizeof(struct ethhdr) + 2 + cur_len);
+ 
+       skb_reserve(frame, hlen + sizeof(struct ethhdr) + 2);
+-      skb_copy_bits(skb, offset, skb_put(frame, len), len);
++      skb_copy_bits(skb, offset, skb_put(frame, cur_len), cur_len);
++
++      len -= cur_len;
++      if (!len)
++              return frame;
++
++      offset += cur_len;
++      __ieee80211_amsdu_copy_frag(skb, frame, offset, len);
+ 
+       return frame;
+ }
+@@ -676,6 +746,7 @@ void ieee80211_amsdu_to_8023s(struct sk_
+       u8 *payload;
+       int offset = 0, remaining, err;
+       struct ethhdr eth;
++      bool reuse_frag = skb->head_frag && !skb_has_frag_list(skb);
+       bool reuse_skb = false;
+       bool last = false;
+ 
+@@ -703,12 +774,13 @@ void ieee80211_amsdu_to_8023s(struct sk_
+               offset += sizeof(struct ethhdr);
+               /* reuse skb for the last subframe */
+               last = remaining <= subframe_len + padding;
+-              if (!skb_is_nonlinear(skb) && last) {
++              if (!skb_is_nonlinear(skb) && !reuse_frag && last) {
+                       skb_pull(skb, offset);
+                       frame = skb;
+                       reuse_skb = true;
+               } else {
+-                      frame = __ieee80211_amsdu_copy(skb, hlen, offset, len);
++                      frame = __ieee80211_amsdu_copy(skb, hlen, offset, len,
++                                                     reuse_frag);
+                       if (!frame)
+                               goto purge;
+