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Date:      Mon, 03 Jul 2000 01:20:15 -0700
From:      David Greenman <dg@root.com>
To:        Bosko Milekic <bmilekic@dsuper.net>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: mbuf re-write(s), v 0.1 
Message-ID:  <200007030820.BAA09516@implode.root.com>
In-Reply-To: Your message of "Mon, 03 Jul 2000 02:03:27 EDT." <Pine.BSF.4.21.0007030136320.2431-100000@jehovah.technokratis.com> 

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>	I'm getting the unfortunate impression that evolution is being
>  frowned upon here. Are their other people that frown the proposal out
>  there to this extent? (i.e. "don't change it if it works") I'd like to
>  hear some important voices on this issue so that I can decide whether to
>  just drop this entire thing and forget about it. (in other words, what do
>  committers and/or core have to say about this?)
>
>  	Aside from this, I've gotten several other "pro" opinions on this;
>  some people have even sent suggestions. So I know that I am not the only
>  one (not by far, in fact) to see an opportunity to benefit from this.
>  Either way, I know *I* will be using this code in time to come, so I
>  suppose the question is:
>	Would you consider committing this code or should I stop posting any
>	changes I make in the future altogether?

   What I'm doing is challenging your assertions that spending CPU cycles to
save memory in the networking code is the right thing to do. I'm further
saying that I have direct experiance in this area since I'm one of the primary
people in FreeBSD's history that have spent major amounts of effort in
improving its performance, especially in the networking area. We (actually
John Dyson and I) made a conscience decision to waste memory in trade for
performance and if we (FreeBSD developers in general) decide to go in the
opposite direction, then it sure ought to be well thought out and have solid
reasoning behind it. In our discussions so far, I haven't yet seen any real
numbers to back up the claims. What is needed is: 1) Some numbers that show
that the memory wastage is significant - and I'm talking about multiple
megabytes at least. If its not 'significant' by that definition (and in my
experiance it isn't), than I'd like to hear why you think much smaller numbers
are significant. 2) I'd like to see some more numbers that show that the
additional CPU wastage is very minimal (say less than 1% of the total amount
of time spent doing the allocs/frees).
   I'm not trying to 'frown upon evolution', unless the particular form of
evolution is to make the software worse than it was. I *can* be convinced
that your proposed changes are a good thing and I'm asking you to step up
to the plate and prove it.

-DG

David Greenman
Co-founder, The FreeBSD Project - http://www.freebsd.org
Manufacturer of high-performance Internet servers - http://www.terasolutions.com
Pave the road of life with opportunities.


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