2016-02-08 13:34:45

by Felix Fietkau

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]>
---
net/wireless/util.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 77 insertions(+), 5 deletions(-)

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 9880c89..c7f6820 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -644,23 +644,93 @@ int ieee80211_data_from_8023(struct sk_buff *skb, const u8 *addr,
}
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_buff *skb, struct sk_buff_head *list,
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_buff *skb, struct sk_buff_head *list,
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;

--
2.2.2

2016-02-23 10:02:35

by Johannes Berg

Subject: Re: [PATCH] cfg80211: reuse existing page fragments in A-MSDU rx

On Mon, 2016-02-08 at 14:34 +0100, Felix Fietkau wrote:
> This massively reduces data copying and thus improves rx performance
>
Applied.

johannes