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authorDavid S. Miller <davem@davemloft.net>2005-07-05 15:17:25 -0700
committerDavid S. Miller <davem@davemloft.net>2005-07-05 15:17:25 -0700
commitc65f7f00c587828e3d50737805a78f74804972de (patch)
tree160f85e7d9ec1df2432b4dd3fae315812558bd10 /net/ipv4
parentb8259d9ad1d0f8d0c5ea0e37bb15080b0bd395b5 (diff)
downloadlinux-stericsson-c65f7f00c587828e3d50737805a78f74804972de.tar.gz
[TCP]: Simplify SKB data portion allocation with NETIF_F_SG.
The ideal and most optimal layout for an SKB when doing scatter-gather is to put all the headers at skb->data, and all the user data in the page array. This makes SKB splitting and combining extremely simple, especially before a packet goes onto the wire the first time. So, when sk_stream_alloc_pskb() is given a zero size, make sure there is no skb_tailroom(). This is achieved by applying SKB_DATA_ALIGN() to the header length used here. Next, make select_size() in TCP output segmentation use a length of zero when NETIF_F_SG is true on the outgoing interface. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/tcp.c13
1 files changed, 2 insertions, 11 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 882436da9a3a..be354155b2f9 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -756,13 +756,9 @@ static inline int select_size(struct sock *sk, struct tcp_sock *tp)
{
int tmp = tp->mss_cache_std;
- if (sk->sk_route_caps & NETIF_F_SG) {
- int pgbreak = SKB_MAX_HEAD(MAX_TCP_HEADER);
+ if (sk->sk_route_caps & NETIF_F_SG)
+ tmp = 0;
- if (tmp >= pgbreak &&
- tmp <= pgbreak + (MAX_SKB_FRAGS - 1) * PAGE_SIZE)
- tmp = pgbreak;
- }
return tmp;
}
@@ -872,11 +868,6 @@ new_segment:
tcp_mark_push(tp, skb);
goto new_segment;
} else if (page) {
- /* If page is cached, align
- * offset to L1 cache boundary
- */
- off = (off + L1_CACHE_BYTES - 1) &
- ~(L1_CACHE_BYTES - 1);
if (off == PAGE_SIZE) {
put_page(page);
TCP_PAGE(sk) = page = NULL;