[Xorp-hackers] Limitations for multiple instances of XORP

[Bruce M Simpson]

Kaplan, Michael A wrote:
>
> I am running multiple instances of XORP on a single machine. I’m 
> looking for some data points in regards to how many instances a system 
> can handle before keeling over. Has anyone else experimented in 
> running multiple XORP instances?
>  
>

Haven't done this myself, although it is definitely a research topic.

A lot of work has gone into making it possible to run XORP virtual 
routers for simulation purposes, and I believe this is what some of Mark 
Handley's students at UCL have been involved with, perhaps they will 
chime in.

What I can tell you is that the sizable runtime memory footprint is 
going to have an effect -- the short answer is, try it and see. You say 
nothing about the size of this machine you're running XORP on, which 
XORP processes you are running, how you've built/linked them, so 
anything here is pure speculation without real data.

But I've just had some coffee, so I'll wax lyrical.

ELF lazy symbol binding will probably have a negligible effect on 
runtime performance, when executables are first loaded.

Sure, page sharing will be a factor at the single executable level, but 
it's not the same as benchmarking the actual reduction in footprint when 
shared libraries are introduced across the board, something I did last 
year but haven't published.

I've done work on reducing this in build engineering land, by rototiling 
for shared libraries, something which people don't seem to want to get 
involved with ("Help me Obi-Wanken Autotools, you're my only hope") 
judging by the burgeoning silence on the topic -- or, perhaps it's more 
open source tragedy of the commons, what can we get for nothing this 
week/month?

[Cue slapstick humour]

The lack of progress is understandably so, given that the quality of the 
freely available tools has only recently come to the point where doing 
it for a moderately sized software project such as XORP, has been 
feasible, i.e. Boost.Build.

Also it qualifies as an "engineering topic", so academics don't get 
rewarded for writing papers about it.

regards
BMS