Re: Make ipconfig.c work as a loadable module.

Eric W. Biederman
2003-03-08T01:53:33Z

Bogdan Costescu <bogdan.costescu@iwr.uni-heidelberg.de> writes:

> On Fri, 7 Mar 2003, Russell King wrote:
>
> > Which version is overly bloated?
> > Which version is huge?
> > Which version is compact?
>
> ... and the size is not important only because we want to make everything
> smaller, but because of how it's commonly used (at least in the clustering
> world from which I come):
>
> the mainboard BIOS or NIC PROC contains PXE/DHCP client; data is
> transferred through UDP, with very poor (if any) congestion control.

Only because the implementations suck. See etherboot.

> Congestion control means here both extreme situations: if packets don't
> arrive to the client, it might not ask again, ask only a limited number of
> times or give up after some timeout; if the server has some faster NIC to
> be able to handle more such requests, it might also send too fast for a
> single client which might drop packets. In some cases, if such situation
> occurs, the client just blocks there printing an error message on the
> console, without trying to restart the whole process and the only way to
> make it do something is to press the Reset button or plug in a keyboard...
> When you have tens or hundreds of such nodes, it's not a pleasure !

But this is all before the kernel is loaded. Having booted a 1000 node
cluster with TFTP and DHCP. From a single host with even being in the same
town, I think I have some room to talk.

> Booting a bunch of such nodes would become problematic if they need
> to transfer more data (=initrd) to start the kernel and so network booting
> would become less reliable. Please note that I'm not saying "ipconfig has
> to stay" - just that any solution should not dramatically increase the
> size of data transferred before the jump to kernel code.

Right. But I would suggest fixing your NBP (what PXE load) which must
be < 64K anyway if you have noticeable reliability problems. Not that
I even suggest using PXE for production use anyway. But sometimes
you are stuck with what you can do.

Eric