Iris Simulator Overview Mitchelle Rasquinha CASL, School of ECE Georgia Institute of Technology ece8813a 7 th Sept 2010

Simulator Basics  Network Simulator - Router Micro-architecture design. - Network topology design.  Discrete Event Simulator (DES) - Will highlight specific kernel api’s that need to be used.  Component Library - Interfaces for models such as a buffer, arbiter, crossbar etc are defined. ( Make sure to inherit from these base classes when you add new models.) - As part of the assignment you will need to add a new router model to the component library. 2Georgia Institute of Technology

Simulator Setup  Has been used on Red hat and Ubuntu distributions of linux  Cpp programming language; Compiles with gcc 4.3 and above.  Help at  Doxygen documentation:  Compilation - Download the source from the downloads section (ece8813a_hw1.tgz) - Untar the source - Compile the source - Example run:  How to add new files: Add them to the Makefile.am and use automake or use the auto_gen.sh script. Detailed instructions on the build tools/environment can be found on the wiki page at 3Georgia Institute of Technology

Terminology  Terminals, Interfaces, Routers Georgia Institute of Technology4 T Int Router T I T I Topology: Routers connected to each other via links. Router Buffers RC Unit Arbiters Crossbar Interface Buffers Arbiters Terminal Packet Generators Another Simulator! Components Pseudo-Components

Code Structure  Traces if you are using the trace packet generator for a terminal node.  Config: Simulator knobs.  Refruns: some sample runs and reference outputs.  Frontend: Instantiation of simulator objects and topology creation.  Util: variables for the simulator knobs  data_types: Packet Formats  components: Component Library Models  Routers, Arbiters, Buffers etc.  Interfaces has the base classes for a generic model.  The actual models are in impl Georgia Institute of Technology5

read_config() create_components() connect_components() loop {component_ptr->setup();} Simulator::StopAt(max_sim_time); Simulator::Run(); loop { component_ptr->print_stats(); } delete components(); exit(0); Terminal nodes and time stepped components schedule an event for time = 1. Kernel process event queue. Simulation Methodology  DES: advance simulation by generating future events Simulator::Schedule( Simulator::Now()+1,,, ); Generic Form of schedule used in Iris Simulator::Schedule( Simulator::Now()+1, NetworkComponent::process_event,, IrisEvent*); Georgia Institute of Technology6 main() Kernel processes all events for time=t and then ticks to time=t+1. Order of events at time ‘t’ is dependent on how they were scheduled. time =cycle1 time =cycle2 time =cycle3

Eg: GenericRouterBase Georgia Institute of Technology7 pseudo components event_handlers Simulator call back function

Example Router Model Georgia Institute of Technology8 in_buffer[p0] decoder[p0] swa,vca xbar downstream_credits input_buffer_state[ p0][vc0]

Eg: GenericRouterBase Events Georgia Institute of Technology9 Pipe stages in backward order Incoming interface to the router. Pseudo components have useful functions such as in_buffer[3]->change_push_channel(2); in_buffer[3].push(flit_ptr);

Conclusion  To get started - “GenericRouterBase” add VCT. - “GenericTracePktGen” modify traffic pattern. - Config increase no of vcs and add additional counters.  Existing code has flit level flow control and pkt level flow control. - downstream_credits in router class [ flit level ] - ready_signal in interface class [ pkt level ]  Some debugging hooks already exist - detect_deadlock(); o Break if a flit was sent out and the credit dint comeback for >1000 cycles.  Use the google group for questions - ece8813a-fall2010 ece8813a-fall tar is in the downloads section of the group.  Warning: Get started early! Georgia Institute of Technology10