From: Stephen Hemminger <shemminger@vyatta•com>
To: "David S. Miller" <davem@davemloft•net>
Cc: netdev@vger•kernel.org
Subject: [PATCH 1/7] tcp: fix RTT for quick packets in congestion control
Date: Mon, 14 Mar 2011 10:52:12 -0700 [thread overview]
Message-ID: <20110314175439.285387215@vyatta.com> (raw)
In-Reply-To: 20110314175211.788224699@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 2011-03-14 08:31:35.442834792 -0700
+++ b/net/ipv4/tcp_input.c 2011-03-14 08:31:40.078917049 -0700
@@ -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:[~2011-03-14 18:02 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-14 17:52 [PATCH 0/7] TCP CUBIC Hystart fixes Stephen Hemminger
2011-03-14 17:52 ` Stephen Hemminger [this message]
2011-03-14 17:52 ` [PATCH 2/7] tcp_cubic: fix comparison of jiffies Stephen Hemminger
2011-03-14 17:52 ` [PATCH 3/7] tcp_cubic: make ack train delta value a parameter Stephen Hemminger
2011-03-14 17:52 ` [PATCH 4/7] tcp_cubic: fix clock dependency Stephen Hemminger
2011-03-14 18:51 ` Eric Dumazet
2011-03-14 21:21 ` Stephen Hemminger
2011-03-14 21:37 ` Eric Dumazet
2011-03-14 17:52 ` [PATCH 5/7] tcp_cubic: enable high resolution ack time if needed Stephen Hemminger
2011-03-14 17:52 ` [PATCH 6/7] tcp_cubic: make the delay threshold of HyStart less sensitive Stephen Hemminger
2011-03-14 17:52 ` [PATCH 7/7] tcp_cubic: fix low utilization of CUBIC with HyStart Stephen Hemminger
2011-03-14 22:58 ` [PATCH 0/7] TCP CUBIC Hystart fixes David Miller
2011-03-22 11:34 ` Lucas Nussbaum
2011-03-22 11:35 ` Lucas Nussbaum
2011-03-22 12:05 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110314175439.285387215@vyatta.com \
--to=shemminger@vyatta$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=netdev@vger$(echo .)kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox