2012-03-29 16:47:47 UTC
the dev list before jumping in. The idea is to simulate a networked
system of multiple machines. The networking simulation will be handled
by ns3, a standard networking simulator. Each GEM5 instance will
connect into ns3 using a tap device (I hope to use ethertap.cc for
this) and ns3 will act as a "router" forwarding packets between GEM5
instances. Each machine will be simulated by it's own GEM5 instance in
a separate thread and will hook into ns-3 using a tap device (ns-3 has
some support for this). ns3 is pretty flexible and can simulate
wired/wireless networks, but that should hopefully not matter to GEM5.
The natural question is handling synchronization between the simulated
times in the various GEM5 instances. My idea is to use barrier
synchronization between the various GEM5 instances at periodic time
intervals. Let's assume this time interval is 10 ms. Then each GEM5
instance runs from 0 through 10 ms of simulated time, and then waits
until all other GEM5 instances have finished their 10 ms slice as
well. The process then repeats itself from simulated time 10 to 20 ms.
Consequently, instances don't get out of sync by more than 10 ms at
any point. This interval is tunable, a lower interval gives you more
accuracy but more run time as well.
I realize that determinism is impossible in this framework, but that's
a hit I am willing to take for my work. I wanted to know if there were
any code examples on using ethertap.cc just like etherlink.cc