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 /net/ipv4/tcp_output.c | |
parent | dc83d4d8f6c897022c974a00769b7a6efee6aed8 (diff) | |
download | linux-cd7d8498c9a5d510c64db38d9f4f4fbc41790f09.tar.bz2 |
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 'net/ipv4/tcp_output.c')
-rw-r--r-- | net/ipv4/tcp_output.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index a462fb1db896..4d92703df4c6 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -384,7 +384,7 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags) TCP_SKB_CB(skb)->tcp_flags = flags; TCP_SKB_CB(skb)->sacked = 0; - shinfo->gso_segs = 1; + tcp_skb_pcount_set(skb, 1); shinfo->gso_size = 0; shinfo->gso_type = 0; @@ -972,6 +972,9 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, tcp_skb_pcount(skb)); + /* OK, its time to fill skb_shinfo(skb)->gso_segs */ + skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb); + /* Our usage of tstamp should remain private */ skb->tstamp.tv64 = 0; @@ -1019,11 +1022,11 @@ static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb, /* Avoid the costly divide in the normal * non-TSO case. */ - shinfo->gso_segs = 1; + tcp_skb_pcount_set(skb, 1); shinfo->gso_size = 0; shinfo->gso_type = 0; } else { - shinfo->gso_segs = DIV_ROUND_UP(skb->len, mss_now); + tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now)); shinfo->gso_size = mss_now; shinfo->gso_type = sk->sk_gso_type; } |