From c65f7f00c587828e3d50737805a78f74804972de Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem@davemloft.net>
Date: Tue, 5 Jul 2005 15:17:25 -0700
Subject: [PATCH] [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>
---
include/net/sock.h | 7 +++++--
net/ipv4/tcp.c | 13 ++-----------
2 files changed, 7 insertions(+), 13 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index e593af5b1ecc..7b76f891ae2d 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1134,13 +1134,16 @@ static inline void sk_stream_moderate_sndbuf(struct sock *sk)
static inline struct sk_buff *sk_stream_alloc_pskb(struct sock *sk,
int size, int mem, int gfp)
{
- struct sk_buff *skb = alloc_skb(size + sk->sk_prot->max_header, gfp);
+ struct sk_buff *skb;
+ int hdr_len;
+ hdr_len = SKB_DATA_ALIGN(sk->sk_prot->max_header);
+ skb = alloc_skb(size + hdr_len, gfp);
if (skb) {
skb->truesize += mem;
if (sk->sk_forward_alloc >= (int)skb->truesize ||
sk_stream_mem_schedule(sk, skb->truesize, 0)) {
- skb_reserve(skb, sk->sk_prot->max_header);
+ skb_reserve(skb, hdr_len);
return skb;
}
__kfree_skb(skb);
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;