The Garnet Synthetic Traffic provides a framework for simulating the Garnet network with controlled inputs. This is useful for network testing/debugging, or for network-only simulations with synthetic traffic.
Note: The garnet synthetic traffic injector only works with Garnet_standalone coherence protocol.
configs/example/garnet_synth_traffic.py : file to invoke the network testersrc/cpu/tester/garnet_sythetic_taffic/GarnetSyntheticTraffic.* : files implementing the testerFirst build gem5 with the Garnet_standalone coherence protocol. This protocol is ISA-agnostic, and hence we build it with the NULL ISA.
scons build/NULL/gem5.debug PROTOCOL=Garnet_standalone
Example command:
./build/NULL/gem5.debug configs/example/garnet_synth_traffic.py \ --num-cpus=16 \ --num-dirs=16 \ --network=garnet2.0 \ --topology=Mesh_XY \ --mesh-rows=4 \ --sim-cycles=1000 \ --synthetic=uniform_random \ --injectionrate=0.01
| System Configuration | Description |
|---|---|
--num-cpus | Number of cpus. This is the number of source (injection) nodes in the network. |
--num-dirs | Number of directories. This is the number of destination (ejection) nodes in the network. |
--network | Network model: simple or garnet2.0. Use garnet2.0 for running synthetic traffic. |
--topology | Topology for connecting the cpus and dirs to the network routers/switches. |
--mesh-rows | The number of rows in the mesh. Only valid when --topology is Mesh* MeshDirCorners* |
| Network Configuration | Description |
|---|---|
--router-latency | Default number of pipeline stages in the garnet router. Has to be >= 1. Can be over-ridden on a per router basis in the topology file. |
--link-latency | Default latency of each link in the network. Has to be >= 1. Can be over-ridden on a per link basis in the topology file. |
--vcs-per-vnet | Number of VCs per Virtual Network. |
--link-width-bits | Width in bits for all links inside the garnet network. Default = 128. |
| Traffic Injection Configuration | Description |
|---|---|
--sim-cycles | Total number of cycles for which the simulation should run. |
--synthetic | The type of synthetic traffic to be injected. The following synthetic traffic patterns are currently supported: uniform_random, tornado, bit_complement, bit_reverse, bit_rotation, neighbor, shuffle, and transpose |
--injectionrate | Traffic Injection Rate in packets/node/cycle. It can take any decimal value between 0 and 1. The number of digits of precision after the decimal point can be controlled by --precision which is set to 3 as default in garnet_synth_traffic.py. |
--single-sender-id | Only inject from this sender. To send from all nodes, set to -1. |
--single-dest-id | Only send to this destination. To send to all destinations as specified by the synthetic traffic pattern, set to -1. |
--num-packets-max | Maximum number of packets to be injected by each cpu node. Default value is -1 (keep injecting till sim-cycles). |
--inj-vnet | Only inject in this vnet (0, 1 or 2). 0 and 1 are 1-flit, 2 is 5-flit. Set to -1 to inject randomly in all vnets. |
The synthetic traffic injector is implemente in GarnetSnytheticTraffic.cc. The sequence of steps involved in generating and sending a packet are as follows.
--num-packets-max is non negative, each cpu stops generating new packets after generating --num-packets-max number of packets. The injector terminates after --sim-cycles.--synthetic).ReadReq, or an INST_FETCH, or a WriteReq, and sent to the Ruby Port (src/mem/ruby/system/RubyPort.hh/cc).RubyRequestType:LD, RubyRequestType:IFETCH, and RubyRequestType:ST, respectively, and sends it to the Sequencer, which in turn sends it to the Garnet_standalone cache controller.LD, IFETCH and ST into virtual networks 0, 1 and 2 respectively.LD and IFETCH are injected as control packets (8 bytes), while ST is injected as a data packet (72 bytes).