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Date:      Mon, 2 Jun 2003 13:01:58 -0700
From:      Sean Chittenden <sean@chittenden.org>
To:        Julian Elischer <julian@elischer.org>
Cc:        hackers@freebsd.org
Subject:   Re: Network stack cloning / virtualization patches
Message-ID:  <20030602200158.GH65470@perrin.int.nxad.com>
In-Reply-To: <Pine.BSF.4.21.0305302116350.4662-100000@InterJet.elischer.org>
References:  <20030530133302.A48390@FreeBSD.org> <Pine.BSF.4.21.0305302116350.4662-100000@InterJet.elischer.org>

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> > Has anyone looked at making the patch work with CURRENT?  Does
> > this do anything to degrade performance of UP systems with no (0?)
> > virtualised images running?
> 
> I have been running tests between two machines with this patch
> installed. There is a "per packet" overhead increase of about 1%.
> there is no overhead increase in the per-byte overhead..  in ther
> words, sending 1 byte packets gets about a 1% decrease in throughput
> but sending 8k chunks has almost no overhead increase..
> 
> Both my machines end up maxing out the 100Mb ethernet between them
> before they see any speed difference at high packet sizes.

1% per packet seems a bit high... where is the overhead coming from?
Seems as though there should be less overhead and that lookup of the
necessary components for each vimage could be found with a hash...  I
looked through the patch and couldn't see any places that screamed
optimization.  Is the overhead really just from copying the data of
the vimage around?

> > Does it make the locking situation much worse?  Can it be stripped
> > down to minimal, clean, well-architected diffs to accomplish a
> > centralised goal, rather than a "Network+goodies, random subsystem
> > overhaul"?
> 
> It is unlikely that the patches could be made in smaller orthogonal
> patches. Its kind of "all or nothing".. Either everything is global
> or it is in a structure (per VM).

*nods*  Hrm, it would appear so.

> > If this is your priority patch, hunting down someone with serious
> > network\ stack-fu to review the diff, and whatnot, would probably
> > be a good investment of your time in that regard.
> 
> I'll bepresenting Marco's paper at USENIX on the (ummm 12th I
> think).  His baby is due then so he can't make it..  (whereas mine
> arrived today so I'll be looking for an excuse to be away from the
> house for 2 days ;-)

:)  Congrats (again!)!

Julian, am I safe in assuming that you have an interest in this work?
If not, I may setup a p4 branch to work with and to merge these bits
into -CURRENT if no one else is interested.  -sc

-- 
Sean Chittenden



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