Date: Wed, 19 Feb 2003 16:19:01 -0600 From: Jon Dugan <jdugan@ncsa.uiuc.edu> To: freebsd-net@freebsd.org Subject: Web100 for FreeBSD Message-ID: <20030219221900.GA2596@ncsa.uiuc.edu>
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I am funded to do the FreeBSD implementation of the Web100[1] kernel
intrumentation set (KIS) and already have a small portion of the KIS
implemented. I have several questions and since I have very little
kernel programming experience I would appreciate any input that the more
experienced folks are willing to offer.
My goal with this code is to get it accepted into the FreeBSD tree. So any
advice or critque of implementation or style is actively solicited.
The Linux implementation exposes the KIS variables through the /proc
filesystem. I have chosen to use the sysctl interface for my initial
implementation. So far this is working out well, I am reading 4 variables
about each connection via sysctl. Is sysctl the right way to get this
information? We may poll some of these variables on a second or sub second
interval.
In order to tune a TCP connection it will be necessary to write to some of
the sysctl OIDs. AFAIK only root can write to sysctl. I can see two
alternatives to solving this problem: 1) using a proxy daemon which runs as
root to handle the updates or 2) add a permissions system to sysctl. Option
2 seems like quite a lot of work and I'm not certain it is generally useful.
Any thoughts?
We are interested in receiving asychronous notification of events within a
particular TCP session in userland. I am planning to use the kqueue
mechanism to provide this.
Patches relative to 5.0-RELEASE are available at:
http://rivendell.ncsa.uiuc.edu/~jdugan/web100bsd/
In truth there isn't much to the patches yet, but it demonstrates the
direction I have taken thus far.
1. Some background Web100:
The Web100 project is concerned with improving TCP performance for typical
TCP sessions. As we all know getting TCP to perform well over long, fat
pipes tends to require quite a bit of tuning. Web100 is an effort to
automatically tune TCP connections. To that end Web100 has developed a
TCP Extended Statistic MIB to define what instruments in a TCP stack are
useful for understanding the behavior of TCP sessions. The KIS is the
implementation of this MIB for a particular TCP implementation, currently
the only fully developed KIS is for Linux. With the information exposed
via the KIS the TCP session can be automatically tuned by a user space
process. Information gleaned from the KIS is also useful to diagnosing
many common problems with TCP performance. The Web100 website has further
information, including the code for the Linux implmentation and an IETF
draft of the TCP Extended Statistic MIB. http://www.web100.org/
Jon
--
Jon Dugan | Senior Network Engineer, NCSA Network Research
jdugan@ncsa.uiuc.edu | 269 CAB, 605 E Springfield, Champaign, IL 61820
217-244-7715 | http://www.ncsa.uiuc.edu/~jdugan/
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