netdev.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: David Miller <davem@davemloft.net>
To: jheffner@psc.edu
Cc: ilpo.jarvinen@helsinki.fi, netdev@vger.kernel.org
Subject: Re: [PATCH net-2.6 0/3]: Three TCP fixes
Date: Wed, 05 Dec 2007 02:30:30 -0800 (PST)	[thread overview]
Message-ID: <20071205.023030.125862645.davem@davemloft.net> (raw)
In-Reply-To: <47559FA1.2090104@psc.edu>

From: John Heffner <jheffner@psc.edu>
Date: Tue, 04 Dec 2007 13:42:41 -0500

> Ilpo Järvinen wrote:
> > ...I'm still to figure out why tcp_cwnd_down uses snd_ssthresh/2
> > as lower bound even though the ssthresh was already halved, 
> > so snd_ssthresh should suffice.
> 
> I remember this coming up at least once before, so it's probably worth a 
> comment in the code.  Rate-halving attempts to actually reduce cwnd to 
> half the delivered window.  Here, cwnd/4 (ssthresh/2) is a lower bound 
> on how far rate-halving can reduce cwnd.  See the "Bounding Parameters" 
> section of <http://www.psc.edu/networking/papers/FACKnotes/current/>.

I assume we're talking about the tcp_cwnd_min() usage in
tcp_cwnd_down(), I don't see where it's dividing by two
there.

Anyways, someone please enlighten me and please also cook
up a patch to add the descriptive comment :-)

Thanks!

  parent reply	other threads:[~2007-12-05 10:30 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-04 16:48 [PATCH net-2.6 0/3]: Three TCP fixes Ilpo Järvinen
2007-12-04 16:48 ` [PATCH 1/3] [TCP] FRTO: Use of existing funcs make code more obvious & robust Ilpo Järvinen
2007-12-04 16:48   ` [PATCH 2/3] [TCP]: Move prior_in_flight collect to more robust place Ilpo Järvinen
2007-12-04 16:48     ` [PATCH 3/3] [TCP]: NAGLE_PUSH seems to be a wrong way around Ilpo Järvinen
2007-12-05 10:26       ` David Miller
2007-12-05 11:18         ` Ilpo Järvinen
2007-12-05 11:33           ` David Miller
2007-12-05 10:21     ` [PATCH 2/3] [TCP]: Move prior_in_flight collect to more robust place David Miller
2007-12-05 10:21   ` [PATCH 1/3] [TCP] FRTO: Use of existing funcs make code more obvious & robust David Miller
2007-12-04 18:42 ` [PATCH net-2.6 0/3]: Three TCP fixes John Heffner
2007-12-04 21:10   ` Ilpo Järvinen
2007-12-04 21:17     ` John Heffner
2007-12-04 21:26       ` Ilpo Järvinen
2007-12-05 11:17         ` Alexey Kuznetsov
2007-12-05  2:13       ` Matt Mathis
2007-12-05 10:30   ` David Miller [this message]
2007-12-05 11:30     ` Ilpo Järvinen
2007-12-06  4:56       ` 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=20071205.023030.125862645.davem@davemloft.net \
    --to=davem@davemloft.net \
    --cc=ilpo.jarvinen@helsinki.fi \
    --cc=jheffner@psc.edu \
    --cc=netdev@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).