LAM: Multiple NICs in SMP nodes

Douglas Eadline deadline at
Wed Aug 16 18:09:31 EDT 2000

On Wed, 16 Aug 2000, David van der Spoel wrote:

> Hi,
> This may be a bit off-topic (OS / MPI) but anyway...
> I have a couple (4, soon 8) of SMP machines (dual P3) running RH linux. To
> improve network performance I bought extra network cards, so that all
> machines have two. My main application (molecular simulation) communicates
> in a ring topology most of the time. Dual network cards could be connected
> in a point to point topology for optimal communication, but other
> (non-ring) communication is sometimes necessary as well, so everything is
> connected through a switch running at 100 Mbit full duplex. 
> Now here are the questions:
> Is there a way of binding processes to network cards (in general not in
> Linux as far as I know...), or alternatively,  is there a way to have a
> persistant TCP connection within LAM? As a third alternative: is there
> anyone that has experimented with channel bonding in recent (2.2.16+)
> Linux kernels? Does one need a special switch to use channel bonding?

The following is on PII-Linux RH6.2 system.

I looked at this a while ago and found I could not get LAM to do it.
My idea was that since there are two CPUs on the motherboard and
two network cards (each running a separate network), I tried to
see if I could boot LAM to use both networks. For instance,

I had 4 systems called coyote1, coyote2, coyote3, coyote4
On the second network, there were called coyote1a, coyote2a, 
coyote3a, coyote4a.

I tried a boot schema:


So when LAM tried to start on coyote1a it complained about
the daemon already running. My goal was to fool LAM
and make 4 dual machines look like 8 singles. 

The best I came up with was to do this:


This way if coyote1 needed to send to all the nodes, it could
use two interfaces at the same time.  I tried running the NASA
parallel benchmarks with this, but found no big performance gain.

I have tried channel bonding, it works. However, if you need 
better latency, channel bonding will provide the
same a single network. Throughput however, can be almost double 
a single network card.

Just some random thoughts


> Groeten, David.
> ________________________________________________________________________
> Dr. David van der Spoel		Biomedical center, Dept. of Biochemistry
> s-mail:	Husargatan 3, Box 576,  75123 Uppsala, Sweden
> e-mail: spoel at	www:
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