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authorIlpo Järvinen <ilpo.jarvinen@helsinki.fi>2009-03-14 22:45:16 +0000
committerDavid S. Miller <davem@davemloft.net>2009-03-15 20:09:55 -0700
commit2a3a041c4e2c1685e668b280c121a5a40a029a03 (patch)
treedab327c0cbebec79968c3c2207d064a9152857f0
parent0c54b85f2828128274f319a1eb3ce7f604fe2a53 (diff)
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tcp: cache result of earlier divides when mss-aligning things
The results is very unlikely change every so often so we hardly need to divide again after doing that once for a connection. Yet, if divide still becomes necessary we detect that and do the right thing and again settle for non-divide state. Takes the u16 space which was previously taken by the plain xmit_size_goal. This should take care part of the tso vs non-tso difference we found earlier. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/tcp.h1
-rw-r--r--net/ipv4/tcp.c14
2 files changed, 13 insertions, 2 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index ad2021ccc55a..9d5078bd23a3 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -248,6 +248,7 @@ struct tcp_sock {
/* inet_connection_sock has to be the first member of tcp_sock */
struct inet_connection_sock inet_conn;
u16 tcp_header_len; /* Bytes of tcp header to send */
+ u16 xmit_size_goal_segs; /* Goal for segmenting output packets */
/*
* Header prediction flags
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 886596ff0aae..0db9f3b984f7 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -665,7 +665,7 @@ static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
int large_allowed)
{
struct tcp_sock *tp = tcp_sk(sk);
- u32 xmit_size_goal;
+ u32 xmit_size_goal, old_size_goal;
xmit_size_goal = mss_now;
@@ -676,7 +676,17 @@ static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
tp->tcp_header_len);
xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal);
- xmit_size_goal -= (xmit_size_goal % mss_now);
+
+ /* We try hard to avoid divides here */
+ old_size_goal = tp->xmit_size_goal_segs * mss_now;
+
+ if (likely(old_size_goal <= xmit_size_goal &&
+ old_size_goal + mss_now > xmit_size_goal)) {
+ xmit_size_goal = old_size_goal;
+ } else {
+ tp->xmit_size_goal_segs = xmit_size_goal / mss_now;
+ xmit_size_goal = tp->xmit_size_goal_segs * mss_now;
+ }
}
return xmit_size_goal;