*BSD News Article 73136


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From: "John S. Dyson" <toor@dyson.iquest.net>
Newsgroups: comp.os.linux.networking,comp.unix.bsd.netbsd.misc,comp.unix.bsd.freebsd.misc
Subject: Re: TCP latency
Date: Mon, 08 Jul 1996 08:01:35 -0500
Organization: John S. Dyson's home machine
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Larry McVoy wrote:

> I'll cop to the complaint John made that the tests don't show how the system
> scales.  There are several ways that I could improve things, such as
> 
>         . plot bandwidths & latencies as a function of the number of
>           tests running (scaling) and amount of data transfered (cache vs
>           memory).
> 
>         . Design benchmarks that are closer to what happens in real life
>           (I'm thinking mostly web stuff here - I need a benchmark that
>           connects, transfers a variable amount of data, and disconnects).
> 
MUCH BETTER...

> 
> Moving on: the comment John made about static Linux vs dynamic FreeBSD
> libraries doesn't ring a bell with me.  It's certainly not true for any
> numbers I've published (like in the Usenix paper - that was all dynamic
> on all systems that supported it, including Linux).
>
I have numbers that I am willing to send to you.  See, I track the
performance of FreeBSD very carefully.  I find that lmbench is
useful, but not a total measure of system performance.
 
> You might take a look at how SGI hardware does
> on lmbench and consider that I work for them, and that the numbers are
> obviously unflattering.
> 
I used to work on Tandem OEM'ed boxes using similar processors to SGI,
and I know *exactly* what you are talking about.

> 
> Finally getting to latencies et al.  I think that everyone should print
> out the two long messages from Linus in this thread.  In over ten years
> of working in the OS world, i have never seen a better treatment of
> the issues.  John needs to push that chip off his shoulder and listen
> to what Linus is saying - it has nothing to about Linux vs FreeBSD; it
> has everything to do with what makes sense for an OS, any OS.
> 
Again, using terms like "chip on my shoulder" perpetuates the
myth that I am somehow personally defective.  Please refrain
from personal comments...  However, you are indeed supporting
my position that the benchmark needs to measure something more
"real world."  Thank you.


> TCP latency was in that
> critical path as well.

Linus EQUATED latency with quality.  That is where alot of the
problem was.  I had brought up the notion that there are alot
of other factors associated with quality, and the cheer about
the no-load latency being so low was kind-of overblown.

John