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tcp: fill shinfo->gso_size at last moment 

In commit cd7d8498c9 ("tcp: change tcp_skb_pcount() location") we stored
gso_segs in a temporary cache hot location.

This patch does the same for gso_size.

This allows to save 2 cache line misses in tcp xmit path for
the last packet that is considered but not sent because of
various conditions (cwnd, tso defer, receiver window, TSQ...)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-06-11 09:15:18 -07:00 committed by David S. Miller
parent 5bbb432c89
commit f69ad292cf
3 changed files with 16 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
include/net/tcp.h
View File

@ -730,11 +730,14 @@ struct tcp_skb_cb {
/* 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()
* tcp_gso_segs/size are used in write queue only,
* cf tcp_skb_pcount()/tcp_skb_mss()
*/
__u32 tcp_tw_isn;
__u32 tcp_gso_segs;
struct {
u16 tcp_gso_segs;
u16 tcp_gso_size;
};
};
__u8 tcp_flags; /* TCP header flags. (tcp[13]) */
@ -790,10 +793,10 @@ 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. */
/* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
static inline int tcp_skb_mss(const struct sk_buff *skb)
{
return skb_shinfo(skb)->gso_size;
return TCP_SKB_CB(skb)->tcp_gso_size;
}
/* Events passed to congestion control interface */

8
net/ipv4/tcp_input.c
View File

@ -1316,12 +1316,12 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
* code can come after this skb later on it's better to keep
* setting gso_size to something.
*/
if (!skb_shinfo(prev)->gso_size)
skb_shinfo(prev)->gso_size = mss;
if (!TCP_SKB_CB(prev)->tcp_gso_size)
TCP_SKB_CB(prev)->tcp_gso_size = mss;
/* CHECKME: To clear or not to clear? Mimics normal skb currently */
if (tcp_skb_pcount(skb) <= 1)
skb_shinfo(skb)->gso_size = 0;
TCP_SKB_CB(skb)->tcp_gso_size = 0;
/* Difference in this won't matter, both ACKed by the same cumul. ACK */
TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
@ -2248,7 +2248,7 @@ static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
(oldcnt >= packets))
break;
mss = skb_shinfo(skb)->gso_size;
mss = tcp_skb_mss(skb);
err = tcp_fragment(sk, skb, (packets - oldcnt) * mss,
mss, GFP_ATOMIC);
if (err < 0)

12
net/ipv4/tcp_output.c
View File

@ -402,8 +402,6 @@ static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
*/
static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
{
struct skb_shared_info *shinfo = skb_shinfo(skb);
skb->ip_summed = CHECKSUM_PARTIAL;
skb->csum = 0;
@ -411,7 +409,6 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
TCP_SKB_CB(skb)->sacked = 0;
tcp_skb_pcount_set(skb, 1);
shinfo->gso_size = 0;
TCP_SKB_CB(skb)->seq = seq;
if (flags & (TCPHDR_SYN | TCPHDR_FIN))
@ -1028,8 +1025,9 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
tcp_skb_pcount(skb));
tp->segs_out += tcp_skb_pcount(skb);
/* OK, its time to fill skb_shinfo(skb)->gso_segs */
/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
/* Our usage of tstamp should remain private */
skb->tstamp.tv64 = 0;
@ -1068,8 +1066,6 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
/* Initialize TSO segments for a packet. */
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
{
struct skb_shared_info *shinfo = skb_shinfo(skb);
/* Make sure we own this skb before messing gso_size/gso_segs */
WARN_ON_ONCE(skb_cloned(skb));
@ -1078,10 +1074,10 @@ static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
* non-TSO case.
*/
tcp_skb_pcount_set(skb, 1);
shinfo->gso_size = 0;
TCP_SKB_CB(skb)->tcp_gso_size = 0;
} else {
tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
shinfo->gso_size = mss_now;
TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
}
}