From: Stephen Hemminger <shemminger@linux-foundation.org>
To: "David S. Miller" <davem@davemloft.net>
Cc: Douglas Leith <doug.leith@nuim.ie>, netdev@vger.kernel.org
Subject: [PATCH] TCP: H-TCP maxRTT estimation at startup
Date: Fri, 3 Aug 2007 10:57:56 +0100 [thread overview]
Message-ID: <20070803105756.2f41dc25@oldman.hamilton.local> (raw)
In-Reply-To: <CA61FA76-2C22-4048-B7AC-1D8E9D94868C@nuim.ie>
Small patch to H-TCP from Douglas Leith.
Fix estimation of maxRTT. The original code ignores rtt measurements
during slow start (via the check tp->snd_ssthresh < 0xFFFF) yet this
is probably a good time to try to estimate max rtt as delayed acking
is disabled and slow start will only exit on a loss which presumably
corresponds to a maxrtt measurement. Second, the original code (via
the check htcp_ccount(ca) > 3) ignores rtt data during what it
estimates to be the first 3 round-trip times. This seems like an
unnecessary check now that the RCV timestamp are no longer used
for rtt estimation.
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
--- a/net/ipv4/tcp_htcp.c 2007-08-03 10:51:51.000000000 +0100
+++ b/net/ipv4/tcp_htcp.c 2007-08-03 10:51:53.000000000 +0100
@@ -79,7 +79,6 @@ static u32 htcp_cwnd_undo(struct sock *s
static inline void measure_rtt(struct sock *sk, u32 srtt)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
- const struct tcp_sock *tp = tcp_sk(sk);
struct htcp *ca = inet_csk_ca(sk);
/* keep track of minimum RTT seen so far, minRTT is zero at first */
@@ -87,8 +86,7 @@ static inline void measure_rtt(struct so
ca->minRTT = srtt;
/* max RTT */
- if (icsk->icsk_ca_state == TCP_CA_Open
- && tp->snd_ssthresh < 0xFFFF && htcp_ccount(ca) > 3) {
+ if (icsk->icsk_ca_state == TCP_CA_Open) {
if (ca->maxRTT < ca->minRTT)
ca->maxRTT = ca->minRTT;
if (ca->maxRTT < srtt
next parent reply other threads:[~2007-08-03 9:57 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CA61FA76-2C22-4048-B7AC-1D8E9D94868C@nuim.ie>
2007-08-03 9:57 ` Stephen Hemminger [this message]
2007-08-08 1:29 ` [PATCH] TCP: H-TCP maxRTT estimation at startup David Miller
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