From 329033f645d93b5f9160b9b972dbc5431ad22a33 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 27 Apr 2012 00:38:33 +0000 Subject: [PATCH] tcp: makes tcp_try_coalesce aware of skb->head_frag MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit TCP coalesce can check if skb to be merged has its skb->head mapped to a page fragment, instead of a kmalloc() area. We had to disable coalescing in this case, for performance reasons. We 'upgrade' skb->head as a fragment in itself. This reduces number of cache misses when user makes its copies, since a less sk_buff are fetched. This makes receive and ofo queues shorter and thus reduce cache line misses in TCP stack. This is a followup of patch "net: allow skb->head to be a page fragment" Tested with tg3 nic, with GRO on or off. We can see "TCPRcvCoalesce" counter being incremented. Signed-off-by: Eric Dumazet Cc: Ilpo Järvinen Cc: Herbert Xu Cc: Maciej Żenczykowski Cc: Neal Cardwell Cc: Tom Herbert Cc: Jeff Kirsher Cc: Ben Hutchings Cc: Matt Carlson Cc: Michael Chan Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 55 ++++++++++++++++++++++++++++++++++---------- 1 file changed, 43 insertions(+), 12 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index c93b0cbb7fc1..96a631deb4e6 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4464,10 +4464,12 @@ static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size) */ static bool tcp_try_coalesce(struct sock *sk, struct sk_buff *to, - struct sk_buff *from) + struct sk_buff *from, + bool *fragstolen) { - int len = from->len; + int delta, len = from->len; + *fragstolen = false; if (tcp_hdr(from)->fin) return false; if (len <= skb_tailroom(to)) { @@ -4478,15 +4480,19 @@ static bool tcp_try_coalesce(struct sock *sk, TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq; return true; } + + if (skb_has_frag_list(to) || skb_has_frag_list(from)) + return false; + if (skb_headlen(from) == 0 && - !skb_has_frag_list(to) && - !skb_has_frag_list(from) && (skb_shinfo(to)->nr_frags + skb_shinfo(from)->nr_frags <= MAX_SKB_FRAGS)) { - int delta = from->truesize - ksize(from->head) - - SKB_DATA_ALIGN(sizeof(struct sk_buff)); + WARN_ON_ONCE(from->head_frag); + delta = from->truesize - ksize(from->head) - + SKB_DATA_ALIGN(sizeof(struct sk_buff)); WARN_ON_ONCE(delta < len); +copyfrags: memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags, skb_shinfo(from)->frags, skb_shinfo(from)->nr_frags * sizeof(skb_frag_t)); @@ -4499,6 +4505,20 @@ static bool tcp_try_coalesce(struct sock *sk, to->data_len += len; goto merge; } + if (from->head_frag) { + struct page *page; + unsigned int offset; + + if (skb_shinfo(to)->nr_frags + skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS) + return false; + page = virt_to_head_page(from->head); + offset = from->data - (unsigned char *)page_address(page); + skb_fill_page_desc(to, skb_shinfo(to)->nr_frags, + page, offset, skb_headlen(from)); + *fragstolen = true; + delta = len; /* we dont know real truesize... */ + goto copyfrags; + } return false; } @@ -4540,10 +4560,15 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) end_seq = TCP_SKB_CB(skb)->end_seq; if (seq == TCP_SKB_CB(skb1)->end_seq) { - if (!tcp_try_coalesce(sk, skb1, skb)) { + bool fragstolen; + + if (!tcp_try_coalesce(sk, skb1, skb, &fragstolen)) { __skb_queue_after(&tp->out_of_order_queue, skb1, skb); } else { - __kfree_skb(skb); + if (fragstolen) + kmem_cache_free(skbuff_head_cache, skb); + else + __kfree_skb(skb); skb = NULL; } @@ -4626,6 +4651,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) const struct tcphdr *th = tcp_hdr(skb); struct tcp_sock *tp = tcp_sk(sk); int eaten = -1; + bool fragstolen = false; if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) goto drop; @@ -4672,7 +4698,9 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) goto drop; tail = skb_peek_tail(&sk->sk_receive_queue); - eaten = (tail && tcp_try_coalesce(sk, tail, skb)) ? 1 : 0; + eaten = (tail && + tcp_try_coalesce(sk, tail, skb, + &fragstolen)) ? 1 : 0; if (eaten <= 0) { skb_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); @@ -4699,9 +4727,12 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) tcp_fast_path_check(sk); - if (eaten > 0) - __kfree_skb(skb); - else if (!sock_flag(sk, SOCK_DEAD)) + if (eaten > 0) { + if (fragstolen) + kmem_cache_free(skbuff_head_cache, skb); + else + __kfree_skb(skb); + } else if (!sock_flag(sk, SOCK_DEAD)) sk->sk_data_ready(sk, 0); return; }