From: Stephen Hemminger <shemminger@vyatta•com>
To: davem@davemloft•net, sangtae.ha@gmail•com, rhee@ncsu•edu
Cc: netdev@vger•kernel.org
Subject: [PATCH 1/6] tcp: fix RTT for quick packets in congestion control
Date: Thu, 10 Mar 2011 08:51:23 -0800 [thread overview]
Message-ID: <20110310165328.811355927@vyatta.com> (raw)
In-Reply-To: 20110310165119.224046957@vyatta.com
[-- Attachment #1: tcp-input-rtt.patch --]
[-- Type: text/plain, Size: 967 bytes --]
In the congestion control interface, the callback for each ACK
includes an estimated round trip time in microseconds.
Some algorithms need high resolution (Vegas style) but most only
need jiffie resolution. If RTT is not accurate (like a retransmission)
-1 is used as a flag value.
When doing coarse resolution if RTT is less than a a jiffie
then 0 should be returned rather than no estimate. Otherwise algorithms
that expect good ack's to trigger slow start (like CUBIC Hystart)
will be confused.
Signed-off-by: Stephen Hemminger <shemminger@vyatta•com>
--- a/net/ipv4/tcp_input.c 2011-03-08 11:11:26.093183654 -0800
+++ b/net/ipv4/tcp_input.c 2011-03-08 11:11:46.641404939 -0800
@@ -3350,7 +3350,7 @@ static int tcp_clean_rtx_queue(struct so
net_invalid_timestamp()))
rtt_us = ktime_us_delta(ktime_get_real(),
last_ackt);
- else if (ca_seq_rtt > 0)
+ else if (ca_seq_rtt >= 0)
rtt_us = jiffies_to_usecs(ca_seq_rtt);
}
next prev parent reply other threads:[~2011-03-10 16:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-10 16:51 [PATCH 0/6] TCP CUBIC and Hystart Stephen Hemminger
2011-03-10 16:51 ` Stephen Hemminger [this message]
2011-03-10 16:51 ` [PATCH 2/6] tcp: timestamp code clarification Stephen Hemminger
2011-03-10 16:51 ` [PATCH 3/6] tcp_cubic: fix comparison of jiffies Stephen Hemminger
2011-03-11 9:40 ` Lucas Nussbaum
2011-03-10 16:51 ` [PATCH 4/6] tcp_cubic: make ack train delta value a parameter Stephen Hemminger
2011-03-10 16:51 ` [PATCH 5/6] tcp_cubic: fix clock dependency Stephen Hemminger
2011-03-11 16:26 ` Sangtae Ha
2011-03-10 16:51 ` [PATCH 6/6] tcp_cubic: enable high resolution ack time if needed Stephen Hemminger
2011-03-11 10:28 ` [PATCH 0/6] TCP CUBIC and Hystart Lucas Nussbaum
2011-03-11 10:49 ` Injong Rhee
2011-03-11 15:58 ` Sangtae Ha
2011-03-11 16:08 ` Lucas Nussbaum
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