diff options
| author | Eric Dumazet <edumazet@google.com> | 2014-09-24 04:11:22 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-09-28 16:36:48 -0400 |
| commit | cd7d8498c9a5d510c64db38d9f4f4fbc41790f09 (patch) | |
| tree | 4057e715ca8227a081db71f1ec1359011c5c1a00 /include/net | |
| parent | dc83d4d8f6c897022c974a00769b7a6efee6aed8 (diff) | |
tcp: change tcp_skb_pcount() location
Our goal is to access no more than one cache line access per skb in
a write or receive queue when doing the various walks.
After recent TCP_SKB_CB() reorganizations, it is almost done.
Last part is tcp_skb_pcount() which currently uses
skb_shinfo(skb)->gso_segs, which is a terrible choice, because it needs
3 cache lines in current kernel (skb->head, skb->end, and
shinfo->gso_segs are all in 3 different cache lines, far from skb->cb)
This very simple patch reuses space currently taken by tcp_tw_isn
only in input path, as tcp_skb_pcount is only needed for skb stored in
write queue.
This considerably speeds up tcp_ack(), granted we avoid shinfo->tx_flags
to get SKBTX_ACK_TSTAMP, which seems possible.
This also speeds up all sack processing in general.
This speeds up tcp_sendmsg() because it no longer has to access/dirty
shinfo.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net')
| -rw-r--r-- | include/net/tcp.h | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 4dc6641ee990..02a9a2c366bf 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -698,7 +698,16 @@ static inline u32 tcp_skb_timestamp(const struct sk_buff *skb) struct tcp_skb_cb { __u32 seq; /* Starting sequence number */ __u32 end_seq; /* SEQ + FIN + SYN + datalen */ - __u32 tcp_tw_isn; /* isn chosen by tcp_timewait_state_process() */ + union { + /* Note : tcp_tw_isn is used in input path only + * (isn chosen by tcp_timewait_state_process()) + * + * tcp_gso_segs is used in write queue only, + * cf tcp_skb_pcount() + */ + __u32 tcp_tw_isn; + __u32 tcp_gso_segs; + }; __u8 tcp_flags; /* TCP header flags. (tcp[13]) */ __u8 sacked; /* State flags for SACK/FACK. */ @@ -746,7 +755,17 @@ TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb, */ static inline int tcp_skb_pcount(const struct sk_buff *skb) { - return skb_shinfo(skb)->gso_segs; + return TCP_SKB_CB(skb)->tcp_gso_segs; +} + +static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs) +{ + TCP_SKB_CB(skb)->tcp_gso_segs = segs; +} + +static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs) +{ + TCP_SKB_CB(skb)->tcp_gso_segs += segs; } /* This is valid iff tcp_skb_pcount() > 1. */ |