mubarak committed Jul 07, 2014 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ``````*** README file for dragonfly network model *** This file describes the setup and configuration for the ROSS dragonfly network model. 1- Model of the dragonfly network topology The dragonfly is a hierarchical topology having several groups connected by all-to-all links. Each router has “p” number of compute nodes connected to it, and there are “a” routers in each group. Routers within a group are connected via local channels. Each router has “h” global channels, which are intergroup connections through which routers in a group connect to routers in other groups. Thus, the radix of each router is k = a + p + h − 1. For load balancing the network traffic, the recommended dragonfly configuration is a = 2p = 2h. Overall, the total number of groups “g” in the network is g = a ∗ h+1. Since each group has “p” nodes and “a” routers, the total number of nodes ’N’ in the network is determined by N = p ∗ a ∗ g. Our ROSS dragonfly model uses the configuration a=2p=2h for modeling the dragonfly topology. Full-sized network packets (default size: 512 bytes) are `````` Misbah Mubarak committed Jan 04, 2016 19 20 ``````broken into smaller flits (default size: 32 bytes) for transportation over the network. ROSS dragonfly model supports four different forms of `````` mubarak committed Jul 07, 2014 21 22 ``````routing: minimal: packet is sent directly from the source group to destination group over the single global channel connecting the source and destination `````` Misbah Mubarak committed Jan 04, 2016 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 ``````groups. non-minimal: packet is first sent to a randomly selected intermediate group and then to the destination group. This type of routing helps to load balance the network traffic under some traffic patterns which congest the single global channel connecting the two groups. adaptive routing: a congestion sensing algorithm is used to choose the minimal or non-minimal path for the packet. progressive adaptive routing: decision to take minimal route is re-assessed as long as the packet stays in the source group. A credit-based flow control system is used to maintain congestion control in the dragonfly. In credit-based flow control, the upstream node/routers keep a count of free buffer slots in the downstream nodes/routers. If buffer space is not available for the next channel, the flit is placed in a pending queue until a credit arrives for that channel. When using non-minimal or adaptive routing, each flit is forwarded to a random global channel due to which the flits may arrive out-of-order at the receiving destination node LP. Therefore, we keep a count of the flits arriving at the destination dragonfly node LP and once all flits of a message arrive, an event is invoked at the corresponding model-net LP, which notifies the higher level MPI simulation layer about message arrival. `````` mubarak committed Jul 07, 2014 43 44 45 46 47 48 49 `````` ROSS models are made up of a collection of logical processes (LPs). Each LP models a distinct component of the system. LPs interact with one another through events in the form of timestamped messages.In the dragonfly model, each LP represents an individual router or node and each time-stamped message represents a packet sent to/from a node/router. `````` 50 ``````2- Configuring CODES dragonfly network model `````` mubarak committed Jul 07, 2014 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 ``````CODES dragonfly network model can be configured using the dragonfly config file (currently located in codes-net/tests/conf). To adjust the network size, configure the MODELNET_GRP section of the config file as well as the 'num_routers' parameter in the PARAMS section in the config file. For example, for a dragonfly configuration of a=8, p=4, h=4, we have 33 groups (g=a*h+1=8*4+1), 264 routers (total_routers=a*g=4*33=264), 1056 network nodes (total_nodes= p*a*g=8*4*33). This configuration can be specified in the config file in the following way MODELNET_GRP { repetitions="264"; server="4"; modelnet_dragonfly="4"; dragonfly_router="1"; } PARAMS { .... num_routers="8"; .... } The first section, MODELNET_GRP specified the number of LPs and the layout of LPs. In the above case, there are 264 repetitions of 4 server LPs, 4 dragonfly network node LPs and 1 dragonfly router LP, which makes a total of 264 routers, 1056 network nodes and 1056 servers in the network. The second section, PARAMS uses 'num_routers' for the dragonfly topology lay out and setsup the connections between routers, network nodes and the servers. Some other dragonfly specific parameters in the PARAMS section are `````` Misbah Mubarak committed Jan 04, 2016 80 ``````- local_vc_size: Bytes (default: 8 KiB) that can fit in the channel connecting routers `````` mubarak committed Jul 07, 2014 81 ``````within the same group. `````` Misbah Mubarak committed Jan 04, 2016 82 83 84 ``````- chunk_size: A full-sized packet of 'packet_size' is divided into smaller flits for transporation (default set to 64 bytes). - global_vc_size: Bytes (default: 16 KiB) that can fit in the global channel connecting `````` mubarak committed Jul 07, 2014 85 ``````two groups with each other. `````` Misbah Mubarak committed Jan 04, 2016 86 ``````- cn_vc_size: Bytes (default: 8 KiB) that can fit in the channel connecting the network `````` mubarak committed Jul 07, 2014 87 ``````node with its router. `````` Misbah Mubarak committed Jul 23, 2015 88 ``````- local_bandwidth: bandwidth of the channels in GiB/sec connecting the routers within the same group. `````` Misbah Mubarak committed Jan 04, 2016 89 90 91 ``````- global_bandwidth: bandwidth of the global channels in GiB/sec connecting routers of two different groups. Note that each router has 'h' number of global channels connected to it where a=2p=2h in our configuration. `````` mubarak committed Jul 07, 2014 92 93 ``````- cn_bandwidth: bandwidth of the channel connecing the compute node with the router. ** All the above bandwidth parameters are in Gigabytes/sec. `````` Misbah Mubarak committed Jan 04, 2016 94 95 ``````- routing: the routing algorithm can be minimal, nonminimal, adaptive or prog-adaptive. `````` mubarak committed Jul 07, 2014 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 `````` 3- Running ROSS dragonfly network model - To run the dragonfly network model with the model-net test program, the following options are available ROSS serial mode: ./tests/modelnet-test --sync=1 -- tests/conf/modelnet-test-dragonfly.conf ROSS conservative mode: mpirun -np 8 tests/modelnet-test --sync=2 -- tests/conf/modelnet-test-dragonfly.conf ROSS optimistic mode: mpirun -np 8 tests/modelnet-test --sync=3 -- tests/conf/modelnet-test-dragonfly.conf 4- Performance optimization tips for ROSS dragonfly model - For large-scale dragonfly runs, the model has significant speedup in optimistic mode than the conservative mode. `````` Misbah Mubarak committed Jan 04, 2016 114 115 ``````- For running large-scale synthetic traffic workloads, see codes-net/src/models/network-workloads/README_synthetic.txt``````