Difference between revisions of "Garnet Synthetic Traffic"

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(Created page with "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 s...")
 
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  | '''--network''' || Network model: simple or garnet2.0. Use garnet2.0 for running synthetic traffic.
 
  | '''--network''' || Network model: simple or garnet2.0. Use garnet2.0 for running synthetic traffic.
 
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  | '''--topology''' || Topology for connecting the cpus and dirs to the network routers/switches. The ''Mesh_XY'' topology creates a network with ''--num-cpus'' number of routers/switches. It requires equal number of cpus and dirs, and connects one cpu, and one dir each to one network router. It weighs the links for XY routing. More detail about different topologies can be found [[Interconnection_Network#Topology|here]].
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  | '''--topology''' || Topology for connecting the cpus and dirs to the network routers/switches. More detail about different topologies can be found [[Interconnection_Network#Topology|here]].
 
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  | '''--mesh-rows''' || The number of rows in the mesh. Only valid when ''--topology'' is ''Mesh_*'' or ''MeshDirCorners_*''.
 
  | '''--mesh-rows''' || The number of rows in the mesh. Only valid when ''--topology'' is ''Mesh_*'' or ''MeshDirCorners_*''.

Revision as of 02:55, 12 September 2016

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. The injector only works with the Garnet_standalone coherence protocol.

Related Files

  • configs/example/garnet_synth_traffic.py: file to invoke the network tester
  • src/cpu/testers/garnet_synthetic_traffic: files implementing the tester.
    • GarnetSyntheticTraffic.py
    • GarnetSyntheticTraffic.hh
    • GarnetSyntheticTraffic.cc


How to run

First build gem5 with the Garnet_standalone coherence protocol:

scons build/Garnet_standalone/gem5.debug

Example command:

./build/Garnet_standalone/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
 

Parameterized Options

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. More detail about different topologies can be found here.
--mesh-rows The number of rows in the mesh. Only valid when --topology is Mesh_* or 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 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.

Implementation of Garnet synthetic traffic

The synthetic traffic injector is implemented in GarnetSyntheticTraffic.cc. The sequence of steps involved in generating and sending a packet are as follows.

  • Every cycle, each cpu performs a bernouli trial with probability equal to --injectionrate to determine whether to generate a packet or not.
  • If --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.
  • If the cpu has to generate a new packet, it computes the destination for the new packet based on the synthetic traffic type (--synthetic).
  • This destination is embedded into the bits after block offset in the packet address.
  • The generated packet is randomly tagged as a ReadReq, or an INST_FETCH, or a WriteReq, and sent to the Ruby Port (src/mem/ruby/system/RubyPort.hh/cc).
  • The Ruby Port converts the packet into a 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.
  • The cache controller extracts the destination directory from the packet address.
  • The cache controller injects the 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).
  • The packet traverses the network and reaches the directory.
  • The directory controller simply drops it.