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Re: [RFC] TCP congestion schedulers

To: Andi Kleen <ak@xxxxxx>
Subject: Re: [RFC] TCP congestion schedulers
From: John Heffner <jheffner@xxxxxxx>
Date: Fri, 8 Apr 2005 15:33:44 -0400 (EDT)
Cc: Stephen Hemminger <shemminger@xxxxxxxx>, netdev@xxxxxxxxxxx
In-reply-to: <m13bur5qyo.fsf@muc.de>
References: <421CF5E5.1060606@ev-en.org> <20050223135732.39e62c6c.davem@davemloft.net> <421D1E66.5090301@osdl.org> <421D30FA.1060900@ev-en.org> <20050225120814.5fa77b13@dxpl.pdx.osdl.net> <20050309210442.3e9786a6.davem@davemloft.net> <4230288F.1030202@ev-en.org> <20050310182629.1eab09ec.davem@davemloft.net> <20050311120054.4bbf675a@dxpl.pdx.osdl.net> <20050311201011.360c00da.davem@davemloft.net> <20050314151726.532af90d@dxpl.pdx.osdl.net> <m13bur5qyo.fsf@muc.de>
Sender: netdev-bounce@xxxxxxxxxxx
On Sat, 19 Mar 2005, Andi Kleen wrote:

> Stephen Hemminger <shemminger@xxxxxxxx> writes:
>
> > Since developers want to experiment with different congestion
> > control mechanisms, and the kernel is getting bloated with overlapping
> > data structure and code for multiple algorithms; here is a patch to
> > split out the Reno, Vegas, Westwood, BIC congestion control stuff
> > into an infrastructure similar to the I/O schedulers.
>
> [...]
>
> Did you do any benchmarks to check that wont slow it down?
>
> I would recommend to try it on a IA64 machine if possible. In the
> past we found that adding indirect function calls on IA64 to networking
> caused measurable slowdowns in macrobenchmarks.
> In that case it was LSM callbacks, but your code looks like it will
> add even more.


For the record, here are some benchmarks from an ia64 over GigE.  I
set the MTU to 564 so it actually stressed the CPU.  Numbers are
throughput (10^6 bits/sec).

Command line used: netperf -H 192.168.1.3 -l -1000000000 -c -C -v 2.

The sender was a 1-CPU 900 MHz Itanium2.  The receiver was a 1-CPU 2.4 GHz
Pentium 4.  The sender reported over 99% utilization; the receiver
reported about 50%.  The NICs were both fiber SysKonnect 9843's connected
back to back.

   Normal reno    Modular reno
        392.77          392.59
        393.96          393.66
        393.22          393.72
        393.12          393.81
        392.09          393.37
        393.3           393.58
        391.81          393.22
        393.11          394.1
        391.32          393.77
        392.94          393.03

average 392.76          393.49
stdev   0.79            0.44

  -John

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