From: Eric Dumazet Date: Mon, 22 Sep 2014 23:29:32 +0000 (-0700) Subject: net: introduce __skb_header_release() X-Git-Tag: v3.18-rc1~115^2~142 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f4a775d14489a801a5b8b0540e23ab82e2703091;p=platform%2Fkernel%2Flinux-exynos.git net: introduce __skb_header_release() While profiling TCP stack, I noticed one useless atomic operation in tcp_sendmsg(), caused by skb_header_release(). It turns out all current skb_header_release() users have a fresh skb, that no other user can see, so we can avoid one atomic operation. Introduce __skb_header_release() to clearly document this. This gave me a 1.5 % improvement on TCP_RR workload. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f1bfa37..8eaa624 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1083,6 +1083,7 @@ static inline int skb_header_cloned(const struct sk_buff *skb) * Drop a reference to the header part of the buffer. This is done * by acquiring a payload reference. You must not read from the header * part of skb->data after this. + * Note : Check if you can use __skb_header_release() instead. */ static inline void skb_header_release(struct sk_buff *skb) { @@ -1092,6 +1093,20 @@ static inline void skb_header_release(struct sk_buff *skb) } /** + * __skb_header_release - release reference to header + * @skb: buffer to operate on + * + * Variant of skb_header_release() assuming skb is private to caller. + * We can avoid one atomic operation. + */ +static inline void __skb_header_release(struct sk_buff *skb) +{ + skb->nohdr = 1; + atomic_set(&skb_shinfo(skb)->dataref, 1 + (1 << SKB_DATAREF_SHIFT)); +} + + +/** * skb_shared - is the buffer shared * @skb: buffer to check * diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 06a8feb..512dc7d 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3179,7 +3179,7 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb) skb_shinfo(nskb)->frag_list = p; skb_shinfo(nskb)->gso_size = pinfo->gso_size; pinfo->gso_size = 0; - skb_header_release(p); + __skb_header_release(p); NAPI_GRO_CB(nskb)->last = p; nskb->data_len += p->len; @@ -3211,7 +3211,7 @@ merge: else NAPI_GRO_CB(p)->last->next = skb; NAPI_GRO_CB(p)->last = skb; - skb_header_release(skb); + __skb_header_release(skb); lp = p; done: diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 070aeff..553b01f 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -609,7 +609,7 @@ static inline bool forced_push(const struct tcp_sock *tp) return after(tp->write_seq, tp->pushed_seq + (tp->max_window >> 1)); } -static inline void skb_entail(struct sock *sk, struct sk_buff *skb) +static void skb_entail(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); @@ -618,7 +618,7 @@ static inline void skb_entail(struct sock *sk, struct sk_buff *skb) tcb->seq = tcb->end_seq = tp->write_seq; tcb->tcp_flags = TCPHDR_ACK; tcb->sacked = 0; - skb_header_release(skb); + __skb_header_release(skb); tcp_add_write_queue_tail(sk, skb); sk->sk_wmem_queued += skb->truesize; sk_mem_charge(sk, skb->truesize); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 8c61a7c..f173b1c 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -995,7 +995,7 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) /* Advance write_seq and place onto the write_queue. */ tp->write_seq = TCP_SKB_CB(skb)->end_seq; - skb_header_release(skb); + __skb_header_release(skb); tcp_add_write_queue_tail(sk, skb); sk->sk_wmem_queued += skb->truesize; sk_mem_charge(sk, skb->truesize); @@ -1167,7 +1167,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, } /* Link BUFF into the send queue. */ - skb_header_release(buff); + __skb_header_release(buff); tcp_insert_write_queue_after(skb, buff, sk); return 0; @@ -1671,7 +1671,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, tcp_set_skb_tso_segs(sk, buff, mss_now); /* Link BUFF into the send queue. */ - skb_header_release(buff); + __skb_header_release(buff); tcp_insert_write_queue_after(skb, buff, sk); return 0; @@ -2772,7 +2772,7 @@ int tcp_send_synack(struct sock *sk) if (nskb == NULL) return -ENOMEM; tcp_unlink_write_queue(skb, sk); - skb_header_release(nskb); + __skb_header_release(nskb); __tcp_add_write_queue_head(sk, nskb); sk_wmem_free_skb(sk, skb); sk->sk_wmem_queued += nskb->truesize; @@ -2947,7 +2947,7 @@ static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb) struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); tcb->end_seq += skb->len; - skb_header_release(skb); + __skb_header_release(skb); __tcp_add_write_queue_tail(sk, skb); sk->sk_wmem_queued += skb->truesize; sk_mem_charge(sk, skb->truesize);