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

Signed-off-by: Felix Fietkau <[email protected]>

SVN-Revision: 48673

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

@@ -0,0 +1,132 @@
+From: Felix Fietkau <[email protected]>
+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 <[email protected]>
+---
+
+--- 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;
+