From 2a3a041c4e2c1685e668b280c121a5a40a029a03 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@helsinki.fi>
Date: Sat, 14 Mar 2009 22:45:16 +0000
Subject: [PATCH] tcp: cache result of earlier divides when mss-aligning things
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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>
---
include/linux/tcp.h | 1 +
net/ipv4/tcp.c | 14 ++++++++++++--
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;